Processing biomass

ABSTRACT

Biomass feedstocks (e.g., plant biomass, animal biomass, and municipal waste biomass) are processed to produce useful products, such as fuels. For example, systems are described that can convert feedstock materials to a sugar solution, which can then be fermented to produce ethanol. Biomass feedstock is saccharified in a vessel by operation of a jet mixer, the vessel also containing a fluid medium and a saccharifying agent.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/179,995, filed May 20, 2009, and U.S. Provisional ApplicationSer. No. 61/218,832, filed Jun. 19, 2009. The complete disclosure ofeach of these provisional applications is hereby incorporated byreference herein.

BACKGROUND

Cellulosic and lignocellulosic materials are produced, processed, andused in large quantities in a number of applications. Often suchmaterials are used once, and then discarded as waste, or are simplyconsidered to be waste materials, e.g., sewage, bagasse, sawdust, andstover.

Various cellulosic and lignocellulosic materials, their uses, andapplications have been described in U.S. Pat. Nos. 7,307,108, 7,074,918,6,448,307, 6,258,876, 6,207,729, 5,973,035 and 5,952,105; and in variouspatent applications, including “FIBROUS MATERIALS AND COMPOSITES,”PCT/US2006/010648, filed on Mar. 23, 2006, AND “FIBROUS MATERIALS ANDCOMPOSITES,” U.S. Patent Application Publication No. 2007/0045456.

SUMMARY

Generally, this invention relates to processes for saccharifying orliquifying a material, e.g., a cellulosic or lignocellulosic feedstock,by converting the cellulosic portion of the material to low molecularweight sugars, e.g., using an enzyme. The invention also relates toconverting a feedstock to a product, e.g., by fermentation.

The processes disclosed herein can utilize low bulk density materials,for example cellulosic or lignocellulosic feedstocks that have beenphysically pretreated to have a bulk density of less than about 0.5g/cm³, e.g., less than about 0.35 g/cm³, 0.25 g/cm³, 0.20 g/cm³, 0.15g/cm³, 0.10 g/cm³, 0.05 g/cm³ or less, e.g., 0.025 g/cm³.

Such materials can be especially difficult to mix with liquids, e.g.,with water or a solvent system for saccharification, fermentation, orother processing. Due to their low bulk density, the materials tend tofloat to the surface of the liquid rather than being dispersed therein.In some cases, the materials can be hydrophobic, highly crystalline, orotherwise difficult to wet. At the same time, it is desirable to processthe feedstock in a relatively high solids level dispersion, in order toobtain a high final concentration of sugar in the saccharified material,or a high concentration of the desired product after processing (e.g.,of ethanol or other alcohol(s) after fermentation). In some cases,utilizing the methods described herein the solids level of thedispersion during processing can be, for example, at least 20, 25, 30,35, 40, 45, or even at least 50 percent by weight dissolved solids.

The inventors have found that dispersion of a feedstock in a liquidmixture can be enhanced, and as a result the solids level of the mixturecan be increased, by the use of certain mixing techniques and equipment.The mixing techniques and equipment disclosed herein also enhance masstransfer, and as a result reaction rates in a mixture, and avoid orminimize harm to sensitive ingredients of the mixture such asmicroorganisms and enzymes. In particular, jet mixing techniques,including for example jet aeration and jet flow agitation, have beenfound to provide good wetting, dispersion and mechanical disruption. Byincreasing the solids level of the mixture, the process can proceed morerapidly, more efficiently and more cost-effectively, and the resultingconcentration of the final product can be increased.

Some of the processes disclosed herein include saccharification of afeedstock, and transportation of the feedstock from a remote location,e.g., where the feedstock is produced or stored, to the manufacturingfacility. In some cases, saccharification can take place partially orentirely during transport. In such cases, it can be advantageous toprovide mixing, e.g., jet mixing, in the transport vessel. In somecases, saccharification can be completed during transport. In someinstances, fermentation can take place partially or entirely duringtransport.

In some implementations, the process further includes reducing therecalcitrance of a feedstock, before or during saccharification. Theprocess may include the further steps of measuring the lignin content ofthe feedstock and determining whether pretreatment is needed and underwhat conditions based on the measured lignin content.

In one aspect, the invention features a method that includessaccharifying a biomass feedstock by mixing the feedstock with a liquidmedium and a saccharifying agent in a vessel, using a jet mixer.

Some embodiments include one or more of the following features. Thefeedstock can have a bulk density of less than about 0.5 g/cm³. Thefeedstock may be, for example, a cellulosic or lignocellulosic material.The liquid can include water. The saccharifying agent can include anenzyme. The jet mixer may include, for example, a jet-flow agitator, ajet aeration type mixer, or a suction chamber jet mixer. If a jetaeration type mixer is used, it may be used without injection of airthrough the jet mixer. For example, if the jet aeration type mixerincludes a nozzle having a first inlet line and a second inlet line, insome cases both inlet lines are supplied with a liquid. In some cases,mixing comprises adding the feedstock to the liquid medium in incrementsand mixing between additions. The method may further include monitoringthe glucose level of the mixture of feedstock, liquid medium andsaccharifying agent during mixing, and in some cases adding additionalfeedstock and saccharifying agent to the vessel during saccharification.The mixing vessel may be, for example, a tank, rail car or tanker truck.Saccharification can in some cases take place partially or completelyduring transport of the mixture of feedstock, liquid medium andsaccharifying agent. The method may further include adding an emulsifieror surfactant to the mixture in the vessel.

In another aspect, the invention features saccharifying a biomassfeedstock by mixing the feedstock with a liquid medium and asaccharifying agent in a vessel, using a mixer that produces generallytoroidal flow within the vessel.

In some embodiments, the mixer is configured to limit any increase inthe overall temperature of the liquid medium to less than 5° C. over thecourse of mixing. This aspect may also include, in some embodiments, anyof the features discussed above.

In yet a further aspect, the invention features a method that includesconverting a low molecular weight sugar to a product by mixing the lowmolecular weight sugar with a microorganism in a liquid medium, using ajet mixer.

Some embodiments include one or more of the following features. Theliquid medium can include water. The microorganism can include yeast.The jet mixer can include a jet-flow agitator, jet aeration type mixer,or suction chamber jet mixer.

In another aspect, the invention features an apparatus that includes atank, a jet mixer having a nozzle disposed within the tank, a deliverydevice configured to deliver a biomass feedstock to the tank, and adelivery device configured to deliver a metered amount of asaccharifying agent to the tank.

Some embodiments include one or more of the following features. The jetmixer can further include a motor, and the apparatus can further includea device configured to monitor the torque on the motor during mixing.The apparatus can also include a controller that adjusts the operationof the feedstock delivery device and/or the saccharifying agent deliverydevice based on input from the torque-monitoring device.

The invention also features a method that includes saccharifying abiomass feedstock in a vessel to form a saccharified mixture;inoculating the saccharified mixture in the vessel with a microorganism;and allowing the inoculated saccharified mixture to ferment in thevessel.

In some cases, the contents of the vessel are transferred to a transportvessel during fermentation and fermentation continues in the transportvessel. The method may further include agitating the contents of thevessel with a jet mixer during saccharification and fermentation. Insome embodiments, the method further includes monitoring the oxygencontent and ethanol and/or sugar content of the fermenting mixture.

In another aspect, the invention features a fermentation system thatincludes a vessel having a vent; a source of oxygen in communicationwith the vessel; an oxygen monitor configured to monitor the oxygencontent of a liquid in the vessel; and a controller configured to adjustthe oxygen content of the liquid, using the vent and oxygen source, inresponse to input from the oxygen monitor.

The flow rate of oxygen into the vessel, if oxygenation is required, canbe relatively low. For example, the controller may be configured tooxygenate the vessel at a rate of less than 0.2 vvm, e.g., less than0.1, 0.05, 0.025, or even less than 0.01 vvm.

The fermentation system may further include a fermentation monitorconfigured to monitor the sugar concentration and/or ethanolconcentration of the liquid in the vessel; and a controller configuredto stop fermentation based on input received from the fermentationmonitor. In some cases, the system includes a fermentation stoppingmodule configured to stop fermentation in response to a signal receivedfrom the controller.

All publications, patent applications, patents, and other referencesmentioned herein or attached hereto are incorporated by reference intheir entirety for all that they contain.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the enzymatic hydrolysis of celluloseto glucose.

FIG. 2 is a flow diagram illustrating conversion of a feedstock toethanol via production and transport of a glucose solution. FIG. 2A is adiagrammatic illustration of a saccharification system according to oneembodiment.

FIG. 3 is a schematic diagram of an ethanol manufacturing facility thathas been retrofitted to utilize the solutions and suspensions disclosedherein.

FIGS. 4 and 4A are diagrams illustrating jet flow exiting a nozzle.

FIG. 5 is a diagrammatic perspective view of a jet-flow agitatoraccording to one embodiment. FIG. 5A is an enlarged perspective view ofthe impeller and jet tube of the jet-flow agitator of FIG. 5. FIG. 5B isan enlarged perspective view of an alternate impeller.

FIG. 6 is a diagram of a suction chamber jet mixing nozzle according toone embodiment. FIG. 6A is a perspective view of a suction chamber jetmixing system according to another embodiment.

FIG. 7 is a diagrammatic perspective view of a jet mixing nozzle for asuction chamber jet mixing system according to another alternateembodiment.

FIG. 8 is a diagrammatic perspective view of a tank and a jet aerationtype mixing system positioned in the tank, with the tank being shown astransparent to allow the jet mixer and associated piping to be seen.FIG. 8A is a perspective view of the jet mixer used in the jet aerationsystem of FIG. 8. FIG. 8B is a diagrammatic perspective view of asimilar system in which an air intake is provided.

FIG. 9 is a cross-sectional view of a jet aeration type mixer accordingto one embodiment.

FIG. 10 is a cross-sectional view of a jet aeration type mixer accordingto an alternate embodiment.

FIGS. 11-13 are diagrams illustrating alternative flow patterns in tankscontaining different configurations of jet mixers.

FIG. 14 is a diagram illustrating the flow pattern that occurs in a tankduring backflushing according to one embodiment.

FIGS. 15 and 15A show a tanker truck and a rail car, respectively, setup for in-transit mixing using a pulsed air portable mixing system.

FIGS. 16 and 16A are perspective views of two embodiments of mixingheads used in a mixer according to an alternate embodiment.

FIG. 17 is a side view of a jet aeration type system according toanother embodiment, showing a multi-level arrangement of nozzles in atank.

FIGS. 18 and 18A are a diagrammatic top view and a perspective view,respectively, of a device that minimizes hold up along the walls of atank during mixing.

FIGS. 19, 20, and 21-21A are views of various water jet devices thatprovide mixing while also minimizing hold up along the tank walls.

FIG. 22 is a cross-sectional view of a tank having a domed bottom andtwo jet mixers extending into the tank from above.

DETAILED DESCRIPTION

Using the methods described herein, biomass (e.g., plant biomass, animalbiomass, and municipal waste biomass) can be processed to produce usefulintermediates and products such as those described herein. Systems andprocesses are described herein that can use as feedstock materialscellulosic and/or lignocellulosic materials that are readily available,but can be difficult to process by processes such as fermentation. Manyof the processes described herein can effectively lower therecalcitrance level of the feedstock, making it easier to process, suchas by bioprocessing (e.g., with any microorganism described herein, suchas a homoacetogen or a heteroacetogen, and/or any enzyme describedherein), thermal processing (e.g., gasification or pyrolysis) orchemical methods (e.g., acid hydrolysis or oxidation). Biomass feedstockcan be treated or processed using one or more of any of the methodsdescribed herein, such as mechanical treatment, chemical treatment,radiation, sonication, oxidation, pyrolysis or steam explosion. Thevarious treatment systems and methods can be used in combinations oftwo, three, or even four or more of these technologies or othersdescribed herein and elsewhere.

The processes disclosed herein can utilize low bulk density materials,for example cellulosic or lignocellulosic feedstocks that have beenphysically pretreated to have a bulk density of less than about 0.5g/cm³, e.g., less than about 0.35 g/cm³, 0.25 g/cm³, 0.20 g/cm³, 0.15g/cm³, 0.10 g/cm³, 0.05 g/cm³ or less, e.g., 0.025 g/cm³. Bulk densityis determined using ASTM D1895B. Briefly, the method involves filling ameasuring cylinder of known volume with a sample and obtaining a weightof the sample. The bulk density is calculated by dividing the weight ofthe sample in grams by the known volume of the cylinder in cubiccentimeters.

In order to convert the feedstock to a form that can be readilyprocessed, the glucan- or xylan-containing cellulose in the feedstock ishydrolyzed to low molecular carbohydrates, such as sugars, by asaccharifying agent, e.g., an enzyme or acid, a process referred to assaccharification. The low molecular weight carbohydrates can then beused, for example, in an existing manufacturing plant, such as a singlecell protein plant, an enzyme manufacturing plant, or a fuel plant,e.g., an ethanol manufacturing facility.

The materials that include cellulose can be treated with thesaccharifying agent by combining the material and the saccharifyingagent in a liquid medium, e.g., a solvent such as an aqueous solution.The saccharifying agent, material and liquid medium are mixedthoroughly, using one or more mixers having the mixing characteristicsdescribed herein, e.g., one or more jet mixers. In some implementations,the material and/or the saccharifying agent are added incrementallyrather than all at once. For example, a portion of the material can beadded to the liquid medium and mixed with the saccharifying agent untilthe material is at least partially saccharified, at which point a secondportion of the material is added to the mixture. This process cancontinue until a desired sugar concentration is obtained.

Enzymes and biomass-destroying organisms that break down biomass, suchas the cellulose and/or the lignin portions of the biomass, contain ormanufacture various cellulolytic enzymes (cellulases), ligninases orvarious small molecule biomass-destroying metabolites. These enzymes maybe a complex of enzymes that act synergistically to degrade crystallinecellulose or the lignin portions of biomass. Examples of cellulolyticenzymes include: endoglucanases, cellobiohydrolases, and cellobiases(β-glucosidases). Referring to FIG. 1, a cellulosic substrate isinitially hydrolyzed by endoglucanases at random locations producingoligomeric intermediates. These intermediates are then substrates forexo-splitting glucanases such as cellobiohydrolase to produce cellobiosefrom the ends of the cellulose polymer. Cellobiose is a water-soluble1,4-linked dimer of glucose. Finally cellobiase cleaves cellobiose toyield glucose. Suitable cellulases will be discussed herein in a latersection.

The saccharification process can be partially or completely performed(a) in a tank (e.g., a tank having a volume of at least 4000, 40,000,400,000, 4,000,000 or 40,000,000 L) in a manufacturing plant, and/or (b)in transit, e.g., in a rail car, tanker truck, or in a supertanker orthe hold of a ship. The time required for complete saccharification willdepend on the process conditions and the feedstock and enzyme used. Ifsaccharification is performed in a manufacturing plant under controlledconditions, the cellulose may be substantially entirely converted toglucose in about 12-96 hours. If saccharification is performed partiallyor completely in transit, saccharification may take longer.

In some cases, saccharification is performed at a pH of about 4 to 7,e.g., about 4.5 to 6, or about 5 to 6.

It is generally preferred that the final concentration of glucose in thesugar solution be relatively high, e.g., greater than 15%, or greaterthan 20, 30, 40, 50, 60, 70, 80, 90 or even greater than 95% by weight.This reduces the volume to be shipped, and also inhibits microbialgrowth in the solution. After saccharification, the volume of water canbe reduced, e.g., by evaporation or distillation.

A relatively high concentration solution can be obtained by limiting theamount of water added to the feedstock with the enzyme. Theconcentration can also be controlled by controlling how muchsaccharification takes place. For example, concentration can beincreased by adding more feedstock to the solution. Solubility of thefeedstock in the medium can be increased, for example, by increasing thetemperature of the solution, and/or by adding a surfactant as will bediscussed below. For example, the solution can be maintained at atemperature of 40-50° C., 50-60° C., 60-80° C., or even higher.

Referring to FIG. 2, a process for manufacturing an alcohol, e.g.,ethanol, can include, for example, optionally physically pre-treatingthe feedstock, e.g., to reduce its size (step 110), before and/or afterthis treatment, optionally treating the feedstock to reduce itsrecalcitrance (step 112), and saccharifying the feedstock to form asugar solution (step 114). Saccharification can be performed by mixing adispersion of the feedstock in a liquid medium, e.g., water, with anenzyme (step 111), as will be discussed in detail below. During or aftersaccharification, the mixture (if saccharification is to be partially orcompletely performed en route) or solution can be transported, e.g., bypipeline, railcar, truck or barge, to a manufacturing plant (step 116).At the plant, the solution can be bio-processed to produce a desiredproduct, e.g., ethanol (step 118), which is then processed further,e.g., by distillation (step 120). The individual steps of this processwill be described in detail below. If desired, the steps of measuringlignin content (step 122) and setting or adjusting process parameters(step 124) can be performed at various stages of the process, forexample just prior to the process step(s) used to change the structureof the feedstock, as shown. If these steps are included, the processparameters are adjusted to compensate for variability in the lignincontent of the feedstock, as described in U.S. Provisional ApplicationNo. 61/151,724, filed on Feb. 11, 2009, the complete disclosure of whichis incorporated herein by reference.

The mixing step 111 and saccharifying step 114 can be performed using,for example, the system shown in FIG. 2A. This system includes aconveyor 130, which receives feedstock that has been treated to reduceits size and optionally to reduce its recalcitrance (steps 110 and 112above) by a feedstock pretreatment module 132. The feedstock 134 isdelivered to a tank 136, which contains a liquid medium 138, e.g.,water, which is delivered to the tank through a valved piping system(not shown). A dispersing system may be used to facilitate initialdispersion of the feedstock into the liquid medium, e.g., as disclosedin U.S. Provisional Application No. 61/296,658, filed Jan. 20, 2010, thefull disclosure of which is incorporated by reference herein.

A saccharifying agent is delivered to the tank from a hopper 140, whichincludes a metering device 142. The contents of the tank are mixed byone or more jet mixers. A jet mixer 144 is represented diagrammaticallyin FIG. 2A; examples of suitable jet mixers will be described in detailbelow. The jet mixer produces a jet using a motor 146 that drives a pumpand/or a rotor (not shown). The torque exerted by the motor 146correlates with the solids level of the mixture in the tank, which inturn reflects the degree to which the mixture has saccharified. Thetorque is measured by a torque monitor 148, which sends a signal to amotor 150 that drives the conveyor 130 and also to the metering device142 of the hopper 140. Thus, the supply of the treated feedstock and theenzyme can be interrupted and resumed as a function of thesaccharification of the contents of the tank. The data measured by thetorque monitor can also be used to adjust the jet mixer, e.g., to alower RPM for a mixer that utilizes a rotor, or to a lower jet velocityfor a pump-driven mixer. Instead of, or in addition to, the torquemonitor, the system may include an Amp monitor (not shown) that measuresthe full load amperage of the motor. In some cases, the jet mixer mayinclude a variable frequency drive (VFD) to allow the speed of the motorto be adjusted.

The system may also include a heat monitor (not shown) that monitors thetemperature of the liquid medium and adjusts the feed rate of thefeedstock and/or the mixing conditions in response to increases intemperature. Such a temperature feedback loop can be used to prevent theliquid medium from reaching a temperature that will denature the enzyme.

When one or more pumps are used in the systems described herein, it isgenerally preferred that positive displacement (PD) pumps be used, e.g.,progressive cavity or screw-type PD pumps.

In some cases, the manufacturing plant can be, for example, an existinggrain-based or sugar-based ethanol plant or one that has beenretrofitted by removing or decommissioning the equipment upstream fromthe bio-processing system (which in a typical ethanol plant generallyincludes grain receiving equipment, a hammermill, a slurry mixer,cooking equipment and liquefaction equipment). Thus, the feedstockreceived by the plant is input directly into the fermentation equipment.A retrofitted plant is shown schematically in FIG. 3. The use of anexisting grain-based or sugar-based ethanol plant in this manner isdescribed in U.S. Ser. No. 12/704,521, filed Feb. 11, 2010, the fulldisclosure of which is incorporated herein by reference.

In some embodiments, rather than transporting the saccharified feedstock(sugar solution) to a separate manufacturing plant, or even a separatetank, the sugar solution is inoculated and fermented in the same tank orother vessel used for saccharification. Fermentation can be completed inthe same vessel, or can be started in this manner and then completedduring transport as discussed above. Saccharifying and fermenting in asingle tank are described in U.S. Provisional Application No.61/296,673, filed Jan. 20, 2010, the full disclosure of which isincorporated herein by reference.

Generally, the oxygen level in the fermentation vessel should becontrolled, e.g., by monitoring the oxygen level and venting the tank oraerating the mixture as necessary. It is also desirable to monitor thelevel of ethanol in the vessel, so that when the ethanol level begins todrop the fermentation process can be stopped, e.g., by heating or theaddition of sodium bisulfite. Other methods of stopping fermentationinclude adding a peroxide (e.g., peroxy acetic acid or hydrogenperoxide), adding succinic acid or a salt thereof, cooling the contentsof the vessel, or reducing the oxygen sparge rate. Combinations of anytwo or more of these methods may be used. If fermentation is to beconducted or completed during transport, the transportation vessel(e.g., the tank of a rail car or tanker truck) can be fitted with acontrol unit that includes an oxygen monitor and ethanol monitor, and adelivery system for delivering sodium bisulfite (or other fermentationterminating additive) to the tank and/or a system for adjusting theparameters in the tank to stop fermentation.

If desired, jet mixing can be utilized during fermentation, and iffermentation is conducted in the same vessel as saccharification thesame equipment can be utilized. However, in some embodiments jet mixingis not necessary. For example, if fermentation is conducted duringtransport the movement of the rail car or tanker truck may provideadequate agitation.

Mixing Feedstock, Enzyme and Liquid

Mixing Characteristics

Various types of mixing devices are described below, and other mixingdevices may be used. Suitable mixers have in common that they producehigh velocity circulating flow, for example flow in a toroidal orelliptical pattern. Generally, preferred mixers exhibit a high bulk flowrate. Preferred mixers provide this mixing action with relatively lowenergy consumption. It is also generally preferred that the mixerproduce relatively low shear and avoid heating of the liquid medium, asshear and/or heat can deleteriously affect the saccharifying agent (ormicroorganism, e.g., in the case of fermentation). As will be discussedin detail below, some preferred mixers draw the mixture through an inletinto a mixing element, which may include a rotor or impeller, and thenexpel the mixture from the mixing element through an outlet nozzle. Thiscirculating action, and the high velocity of the jet exiting the nozzle,assist in dispersing material that is floating on the surface of theliquid or material that has settled to the bottom of the tank, dependingon the orientation of the mixing element. Mixing elements can bepositioned in different orientations to disperse both floating andsettling material, and the orientation of the mixing elements can insome cases be adjustable.

In some preferred mixing systems the velocity v_(o) of the jet as itmeets the ambient fluid is from about 2 to 300 m/s, e.g., about 5 to 150m/s or about 10 to 100 m/s. The power consumption of the mixing systemmay be about 20 to 1000 KW, e.g., 30 to 570 KW or 50 to 500 KW, or 150to 250 KW for a 100,000 L tank. It is generally preferred that the powerusage be low for cost-effectiveness.

Jet Mixing

Jet mixing involves the discharge of a submerged jet, or a number ofsubmerged jets, of high velocity liquid into a fluid medium, in thiscase the mixture of biomass feedstock, liquid medium and saccharifyingagent. The jet of liquid penetrates the fluid medium, with its energybeing dissipated by turbulence and some initial heat. This turbulence isassociated with velocity gradients (fluid shear). The surrounding fluidis accelerated and entrained into the jet flow, with this secondaryentrained flow increasing as the distance from the jet nozzle increases.The momentum of the secondary flow remains generally constant as the jetexpands, as long as the flow does not hit a wall, floor or otherobstacle. The longer the flow continues before it hits any obstacle, themore liquid is entrained into the secondary flow, increasing the bulkflow in the tank or vessel. When it encounters an obstacle, thesecondary flow will lose momentum, more or less depending on thegeometry of the tank, e.g., the angle at which the flow impinges on theobstacle. It is generally desirable to orient the jets and/or design thetank so that hydraulic losses to the tank walls are minimized. Forexample, it may be desirable for the tank to have an arcuate bottom(e.g., a domed headplate), and for the jet mixers to be orientedrelatively close to the sidewalls, as shown in FIG. 22. The tank bottom(lower head plate) may have any desired domed configuration, or may havean elliptical or conical geometry.

Jet mixing differs from most types of liquid/liquid and liquid/solidmixing in that the driving force is hydraulic rather than mechanical.Instead of shearing fluid and propelling it around the mixing vessel, asa mechanical agitator does, a jet mixer forces fluid through one or morenozzles within the tank, creating high-velocity jets that entrain otherfluid. The result is shear (fluid against fluid) and circulation, whichmix the tank contents efficiently.

Referring to FIG. 4, the high velocity gradient between the core flowfrom a submerged jet and the surrounding fluid causes eddies. FIG. 4Aillustrates the general characteristics of a submerged jet. As thesubmerged jet expands into the surrounding ambient environment thevelocity profile flattens as the distance (x) from the nozzle increases.Also, the velocity gradient dv/dr changes with r (the distance from thecenterline of the jet) at a given distance x, such that eddies arecreated which define the mixing zone (the conical expansion from thenozzle).

In an experimental study of a submerged jet in air (the results of whichare applicable to any fluid, including water), Albertson et al.(“Diffusion of Submerged Jets,” Paper 2409, Amer. Soc. of CivilEngineers Transactions, Vol. 115:639-697, 1950, at p. 657) developeddimensionless relationships for v(x)_(r=0)/v₀ (centerline velocity),v(r)_(x)/v(x)_(r=0) (velocity profile at a given x), Q_(x)/Q_(o) (flowentrainment), and E_(x)/E_(o) (energy change with x):

(1) Centerline velocity, v(x)_(r=0)/v₀:

${\frac{v\left( {r = 0} \right)}{v_{o}}\frac{x}{D_{o}}} = 6.2$

(2) velocity profile at any x, v(r)_(x)/v(x)_(r=0):

${\log \left\lbrack {\frac{{v(r)}_{x}}{v_{o}}\frac{x}{D}} \right\rbrack} = {0.79 - {33\frac{r^{2}}{x^{2}}}}$

(3) Flow and energy at any x:

$\begin{matrix}{\frac{Q_{x}}{Q_{o}} = {0.32\frac{\,^{15}x}{D_{o}}}} & (10.21) \\{\frac{E_{x}}{E_{o}} = {4.1\frac{D_{o}}{x}}} & (10.22)\end{matrix}$

where:

-   v(r=0)=centerline velocity of submerged jet (m/s),-   v_(o)=velocity of jet as it emerges from the nozzle (m/s),-   x=distance from nozzle (m),-   r=distance from centerline of jet (m),-   D_(o)=diameter of nozzle (m),-   Q_(x)=flow of fluid across any given plane at distance x from the    nozzle (me/s),-   Q_(o)=flow of fluid emerging from the nozzle (m3/s),-   E=energy flux of fluid across any given plane at distance x from the    nozzle (m³/s),-   E_(o)=energy flux of fluid emerging from the nozzle (m³/s).

(“Water Treatment Unit Processes: Physical and Chemical,” David W.Hendricks, CRC Press 2006, p. 411.)

Jet mixing is particularly cost-effective in large-volume (over 1,000gal) and low-viscosity (under 1,000 cPs) applications. It is alsogenerally advantageous that in most cases the pump or motor of the jetmixer not be submerged, e.g., when a pump is used it is generallylocated outside the vessel.

One advantage of jet mixing is that the temperature of the ambient fluid(other than directly adjacent the exit of the nozzle, where there may besome localized heating) is increased only slightly if at all. Forexample, the temperature may be increased by less than 5° C., less than1° C., or not to any measureable extent.

Jet-Flow Agitators

One type of jet-flow agitator is shown in FIGS. 4-4A. This type of mixeris available commercially, e.g., from IKA under the tradename ROTOTRON™.Referring to FIG. 4, the mixer 200 includes a motor 202, which rotates adrive shaft 204. A mixing element 206 is mounted at the end of the driveshaft 204. As shown in FIG. 4A, the mixing element 206 includes a shroud208 and, within the shroud, an impeller 210. As indicated by the arrows,when the impeller is rotated in its “forward” direction, the impeller210 draws liquid in through the open upper end 212 of the shroud andforces the liquid out through the open lower end 214. Liquid exiting end214 is in the form of a high velocity stream or jet. If the direction ofrotation of the impeller 210 is reversed, liquid can be drawn in throughthe lower end 214 and ejected through the upper end 212. This can beused, for example, to suck in solids that are floating near or on thesurface of the liquid in a tank or vessel. (It is noted that “upper” and“lower” refer to the orientation of the mixer in FIG. 4; the mixer maybe oriented in a tank so that the upper end is below the lower end.)

The shroud 208 includes flared areas 216 and 218 adjacent its ends.These flared areas are believed to contribute to the generally toroidalflow that is observed with this type of mixer. The geometry of theshroud and impeller also concentrate the flow into a high velocitystream using relatively low power consumption.

Preferably, the clearance between the shroud 208 and the impeller 210 issufficient so as to avoid excessive milling of the material as it passesthrough the shroud. For example, the clearance may be at least 10 timesthe average particle size of the solids in the mixture, preferably atleast 100 times.

In some implementations, the shaft 204 is configured to allow gasdelivery through the shaft. For example, the shaft 204 may include abore (not shown) through which gas is delivered, and one or moreorifices through which gas exits into the mixture. The orifices may bewithin the shroud 208, to enhance mixing, and/or at other locationsalong the length of the shaft 204.

The impeller 210 may have any desired geometry that will draw liquidthrough the shroud at a high velocity. The impeller is preferably amarine impeller, as shown in FIG. 4A, but may have a different design,for example, a Rushton impeller as shown in FIG. 4B, or a modifiedRushton impeller, e.g., tilted so as to provide some axial flow.

In order to generate the high velocity flow through the shroud, themotor 202 is preferably a high speed, high torque motor, e.g., capableof operating at 500 to 20,000 RPM, e.g., 3,000 to 10,000 RPM. However,the larger the mixer (e.g., the larger the shroud and/or the larger themotor) the lower the rotational speed can be. Thus, if a large mixer isused, such as a 5 hp, 10 hp, 20 hp, or 30 hp or greater, the motor maybe designed to operate at lower rotational speeds, e.g., less than 2000RPM, less than 1500 RPM, or even 500 RPM or less. For example, a mixersized to mix a 10,000-20,000 liter tank may operate at speeds of 900 to1,200 RPM. The torque of the motor is preferably self-adjusting, tomaintain a relatively constant impeller speed as the mixing conditionschange over time, e.g., due to saccharification of the solids.

Advantageously, the mixer can be oriented at any desired angle orlocation in the tank, to direct the jet flow in a desired direction.Moreover, as discussed above, depending on the direction of rotation ofthe impeller the mixer can be used to draw fluid from either end of theshroud.

In some implementations, two or more jet mixers are positioned in thevessel, with one or more being configured to jet fluid upward (“uppump”) and one or more being configured to jet fluid downward (“downpump”). In some cases, an up pumping mixer will be positioned adjacent adown pumping mixer, to enhance the turbulent flow created by the mixers.If desired, one or more mixers may be switched between upward flow anddownward flow during processing. It may be advantageous to switch all ormost of the mixers to up pumping mode during initial dispersion of thefeedstock in the liquid medium, particularly if the feedstock is dumpedor blown onto the surface of the liquid, as up pumping createssignificant turbulence at the surface. Up pumping can also be usedduring fermentation to help remove CO₂ from the liquid by causing thegas to bubble to the surface where it can be vented.

Suction Chamber Jet Mixers

Another type of jet mixer includes a primary nozzle that delivers apressurized fluid from a pump, a suction inlet adjacent the primarynozzle through which ambient fluid is drawn by the pressure drop betweenthe primary nozzle and the wider inlet, and a suction chamber extendingbetween the suction inlet and a secondary nozzle. A jet of high velocityfluid exits the secondary nozzle.

An example of this type of mixer is shown in FIG. 6. As shown, in mixer600 pressurized liquid from a pump (not shown) flows through an inletpassage 602 and exits through a primary nozzle 603. Ambient liquid isdrawn through a suction inlet 604 into suction chamber 606 by thepressure drop caused by the flow of pressurized liquid. The combinedflow exits from the suction chamber into the ambient liquid at highvelocity through secondary nozzle 608. Mixing occurs both in the suctionchamber and in the ambient liquid due to the jet action of the exitingjet of liquid.

A mixing system that operates according to a similar principle is shownin FIG. 6A. Mixers embodying this design are commercially available fromITT Water and Wastewater, under the tradename Flygt™ jet mixers. Insystem 618, pump 620 generates a primary flow that is delivered to thetank (not shown) through a suction nozzle system 622. The suction nozzlesystem 622 includes a primary nozzle 624 which functions in a mannersimilar to primary nozzle 603 described above, causing ambient fluid tobe drawn into the adjacent open end 626 of ejector tube 628 due to thepressure drop induced by the fluid exiting the primary nozzle. Thecombined flow then exits the other end 630 of ejector tube 628, whichfunctions as a secondary nozzle, as a high velocity jet.

The nozzle shown in FIG. 7, referred to as an eductor nozzle, operatesunder a similar principle. A nozzle embodying this design iscommercially available under the tradename TeeJet®. As shown, in nozzle700 pressurized liquid flows in through an inlet 702 and exits a primarynozzle 704, drawing ambient fluid in to the open end 706 of a diffuser708. The combined flow exits the opposite open end 710 of the diffuserat a circulation flow rate A+B that is the sum of the inlet flow rate Aand the flow rate B of the entrained ambient fluid.

Jet Aeration Type Mixers

Another type of jet mixing system that can be utilized is referred to inthe wastewater industry as “jet aeration mixing.” In the wastewaterindustry, these mixers are typically used to deliver a jet of apressurized air and liquid mixture, to provide aeration. However, in thepresent application in some cases the jet aeration type mixers areutilized without pressurized gas, as will be discussed below. Theprinciples of operation of jet aeration mixers will be initiallydescribed in the context of their use with pressurized gas, for clarity.

An eddy jet mixer, such as the mixer 800 shown in FIGS. 8-8B, includesmultiple jets 802 mounted in a radial pattern on a central hub 804. Theradial pattern of the jets uniformly distributes mixing energythroughout the tank. The eddy jet mixer may be centrally positioned in atank, as shown, to provide toroidal flow about the center axis of thetank. The eddy jet mixer may be mounted on piping 806, which supplieshigh velocity liquid to the eddy jet mixer. In the embodiment shown inFIG. 8B, air is also supplied to the eddy jet mixer through piping 812.The high velocity liquid is delivered by a pump 808 which is positionedoutside of the tank and which draws liquid in through an inlet 810 inthe side wall of the tank.

FIGS. 9 and 10 show two types of nozzle configurations that are designedto mix a gas and a liquid stream and eject a high velocity jet. Thesenozzles are configured somewhat differently from the eddy jet mixershown in FIGS. 8 and 8A but function in a similar manner. In the system900 shown in FIG. 9, a primary or motive fluid is directed through aliquid line 902 to inner nozzles 904 through which the liquid travels athigh velocity into a mixing area 906. A second fluid, e.g., a gas, suchas compressed air, nitrogen or carbon dioxide, or a liquid, enters themixing area through a second line 908 and entrained in the motive fluidentering the mixing area 906 through the inner nozzles. In someinstances the second fluid is nitrogen or carbon dioxide so as to reduceoxidation of the enzyme. The combined flow from the two lines is jettedinto the mixing tank through the outer nozzles 910. If the second fluidis a gas, tiny bubbles are entrained in the liquid in the mixture.Liquid is supplied to the liquid line 902 by a pump. Gas, if it is used,is provided by compressors. If a liquid is used as the second fluid, itcan have the same velocity as the liquid entering through the liquidline 902, or a different velocity.

FIG. 10 shows an alternate nozzle design 1000, in which outer nozzles1010 (of which only one is shown) are positioned along the length of anelongated member 1011 that includes a liquid line 1002 that ispositioned parallel to a second line 1008. Each nozzle includes a singleouter nozzle 1010 and a single inner nozzle 1004. Mixing of the motiveliquid with the second fluid proceeds in the same manner as in thesystem 900 described above.

FIGS. 11 and 12 illustrate examples of jet aeration type mixing systemsin which nozzles are positioned along the length of an elongated member.In the example shown in FIG. 11, the elongated member 1102 is positionedalong the diameter of the tank 1104, and the nozzles 1106 extend inopposite directions from the nozzle to produce the indicated flowpattern which includes two areas of generally elliptical flow, one oneither side of the central elongated member. In the example shown inFIG. 12, the tank 1204 is generally rectangular in cross section, andthe elongated member 1202 extends along one side wall 1207 of the tank.In this case, the nozzles 1206 all face in the same direction, towardsthe opposite side wall 1209. This produces the flow pattern shown, inwhich flow in the tank is generally elliptical about a major axisextending generally centrally along the length of the tank. In theembodiment shown in FIG. 12, the nozzles may be canted towards the tankfloor, e.g., at an angle of from about 15 to 30 degrees from thehorizontal.

In another embodiment, shown in FIG. 13, the nozzles 1302, 1304, andsuction inlet 1306 are arranged to cause the contents of the tank toboth revolve and rotate in a toroidal, rolling donut configurationaround a central vertical axis of the tank. Flow around the surface ofthe toroid is drawn down the tank center, along the floor, up the wallsand back to the center, creating a rolling helix pattern, which sweepsthe center and prevents solids from settling. The toroidal pattern isalso effective in moving floating solids to the tank center where theyare pulled to the bottom and become homogenous with the tank contents.The result is a continuous helical flow pattern, which minimizes tankdead spots.

Backflushing

In some instances, the jet nozzles described herein can become plugged;which may cause efficiency and cost effectiveness to be reduced.Plugging of the nozzles may be removed by reversing flow of the motiveliquid through the nozzle. For example, in the system shown in FIG. 14,this is accomplished by closing a valve 1402 between the pump 1404 andthe liquid line 1406 flowing to the nozzles 1408, and activating asecondary pump 1410. Secondary pump 1410 draws fluid in through thenozzles. The fluid then travels up through vertical pipe 1412 due tovalve 1402 being closed. The fluid exits the vertical pipe 1412 at itsoutlet 1414 for recirculation through the tank.

Mixing in Transit/Portable Mixers

As noted above, if desired saccharification can take place in part orentirely during transportation of the mixture, e.g., between a firstprocessing plant for treating the feedstock and a second processingplant for production of a final product such as ethanol. In this case,mixing can be conducted using a jet mixer designed for rail car or otherportable use. Examples of such mixers will be discussed below. As showndiagrammatically in FIGS. 15 and 15A, mixers 1602, 1604 can be insertedthrough a port 1606 in a tank, e.g., of a truck (FIG. 15) or a railcar(FIG. 15A). The mixer can be operated using a control system 1608external to the tank, which may include for example a motor and/or asupply or compressed air, depending on the type of mixing system used,and a controller configured to control the operation of the mixer.Venting (not shown) may also be provided.

Other Mixing Systems/Nozzles

Pulsed Air/fluid

An alternative type of mixer utilizes a gas delivered in pulses to themixture. Such a mixer is shown diagrammatically in FIGS. 15 and 15A, asan example of a portable railcar mixer. Metered amounts of high pressuregas are injected or pulsed under flat round discs (accumulator plates)positioned near the tank bottom. The sudden release of air shocks theliquid. As the gas moves outward between the plate and the tank floor,it sweeps out solids that have settled. The gas then accumulates abovethe plate into large, oval shaped bubbles. As each bubble rises to thesurface, it pushes the liquid above it up and out towards the tankperimeter. The liquid moves toward the sides of the tank and travelsdown the tank wall to the bottom. This movement of the bubbles forcessolids to the surface and creates a generally circular or toroidalcirculation of liquid in the tank. The gas may be, for example, air,nitrogen, or carbon dioxide. The tank is vented (not shown) to allow gasto escape from the tank during mixing.

Low Speed Agitators

FIGS. 16 and 16A illustrate agitators configured to be mounted on ashaft (not shown) for rotational mixing at relatively low speeds. Theagitators may include, for example, two mixing elements 1702 (FIG. 16),or three mixing elements (FIG. 16A), mounted on support arms 1701 abouta central mounting hub 1703 that is disposed to receive a shaft.

The mixing elements 1702 are in the form of truncated cones, each ofwhich has a first end 1704 and a second end 1706. The first end has across-section greater than the cross-section of the second end. Themixing elements are positioned such that the central axes of the mixingelements are disposed at an angle relative to a plane of rotation of themixing elements.

The agitator is rotated in a direction so that liquid flows in throughthe first end 1704 and out through the second end 1706 at a highervelocity, creating dynamic flow conditions by generating turbulent flowat the tapered end of each mixing element. The angulation of the mixingelements relative to the plane of rotation tends to cause a continuousclosed circular flow which in the vicinity of an adjacent tank orcontainer wall flows upwardly and in the central part of the tank orcontainer flows downwardly coaxially to the mixer shaft where it passesthrough the intermediate spaces between the support arms 1701. Theintensity of this circular flow depends on the magnitude of the angle.

Mixers of this type are available commercially from Inotec under thetradename Visco-Jet™. Folding mixers are available which can be put inrail car or other transport container. A similar type of mixer isdescribed in U.S. Pat. No. 6,921,194, the full disclosure if which isincorporated herein by reference.

Minimizing Hold Up on Tank Walls

In some situations, in particular at solids levels approaching atheoretical or practical limit, material may accumulate along the sidewall and/or bottom wall of the tank during mixing. This phenomenon,referred to as “hold up,” is undesirable as it can result in inadequatemixing. Several approaches can be taken to minimize hold up and ensuregood mixing throughout the tank.

For example, in addition to the jet mixing device(s), the tank can beoutfitted with a scraping device, for example a device having a bladethat scrapes the side of the tank in a “squeegee” manner. Such devicesare well known, for example in the dairy industry. Suitable agitatorsinclude the side and bottom sweep agitators and scraper blade agitatorsmanufactured by Walker Engineered Products, New Lisbon, Wis. As shown inFIG. 18, a side and bottom sweep agitator 1800 may include a centralelongated member 1802, mounted to rotate about the axis of the tank.Side wall scraper blades 1804 are mounted at each end of the elongatedmember 1802 and are disposed at an angle with respect to the elongatedmember. In the embodiment shown, a pair of bottom wall scraper blades1806 are mounted at an intermediate point on the elongated member 1802,to scrape up any material accumulating on the tank bottom. Thesescrapers may be omitted if material is not accumulating on the tankbottom. As shown in FIG. 18A, the scraper blades 1804 may be in the formof a plurality of scraper elements positioned along the side wall. Inother embodiments, the scraper blades are continuous, or may have anyother desired geometry.

In other embodiments, the jet mixer itself is configured so as tominimize hold up. For example, the jet mixer may include one or moremovable heads and/or flexible portions that move during mixing. Forexample, the jet mixer may include an elongated rotatable member havinga plurality of jet nozzles along its length. The elongated member may beplanar, as shown in FIG. 19, or have a non-planar shape, e.g., it mayconform to the shape of the tank walls as shown in FIG. 20.

Referring to FIG. 19, the jet mixer nozzles may be positioned on arotating elongated member 1900 that is driven by a motor 1902 and shaft1904. Water or other fluid is pumped through passageways in the rotatingmember, e.g., by a pump impeller 1906, and exits as a plurality of jetsthrough jet orifices 1908 while the member 1900 rotates. To reduce holdup on the tank side walls, orifices 1910 may be provided at the ends ofthe member 1900.

In the embodiment shown in FIG. 20, to conform to the particular shapeof the tank 2000 the elongated member includes horizontally extendingarms 2002, downwardly inclined portions 2004, outwardly and upwardlyinclined portions 2006, and vertically extending portions 2008. Fluid ispumped through passageways within the elongated member to a plurality ofjet orifices 38, through which jets are emitted while the elongatedmember is rotated.

In both of the embodiments shown in FIGS. 19 and 20, the jets providemixing while also washing down the side walls of the tank.

In other embodiments, the jet mixer may include flexible members and oradjustable members (e.g., bendable or telescoping tubes) through whichthe jets are delivered. For example, as shown diagrammatically in FIGS.21 and 21A, the jet mixing device may be made up of flexible tubing, inthe manner of a floating type of pool cleaner, such as is disclosed inU.S. Pat. No. 3,883,368. In the system 2100 shown, a flexible supplyhose 2102 delivers fluid from an inlet 2104 in the sidewall of the tank2106. The supply hose 2102 extends along the surface of the liquid inthe tank via a series of buoys 2108 and swivels 2110. A plurality offlexible hoses 2112 are secured at their upper ends to spaced T-joints2114 in the floating portion of the supply hose 2102. Fluid is jettedfrom the open distal ends of the flexible hoses 2112, resulting inmixing of the contents of the tank and removal of hold up on the tankside walls.

In some implementations, combinations of the embodiments described abovemay be used. For example, combinations of planar and non-planar rotatingor oscillating elongated members may be used. The moving nozzlearrangements described above can be used in combination with each otherand/or in combination with scrapers. A plurality of moving nozzlearrangements can be used together, for example two or more of therotating members shown in FIG. 19 can be stacked vertically in the tank.When multiple rotating members are used, they can be configured torotate in the same direction or in opposite directions, and at the samespeed or different speeds.

Materials Biomass Materials

The biomass can be, e.g., a cellulosic or lignocellulosic material. Suchmaterials include paper and paper products (e.g., polycoated paper andKraft paper), wood, wood-related materials, e.g., particle board,grasses, rice hulls, bagasse, jute, hemp, flax, bamboo, sisal, abaca,straw, switchgrass, alfalfa, hay, corn cobs, corn stover, coconut hair;and materials high in α-cellulose content, e.g., cotton. Feedstocks canbe obtained from virgin scrap textile materials, e.g., remnants, postconsumer waste, e.g., rags. When paper products are used they can bevirgin materials, e.g., scrap virgin materials, or they can bepost-consumer waste. Aside from virgin raw materials, post-consumer,industrial (e.g., offal), and processing waste (e.g., effluent frompaper processing) can also be used as fiber sources. Biomass feedstockscan also be obtained or derived from human (e.g., sewage), animal orplant wastes. Additional cellulosic and lignocellulosic materials havebeen described in U.S. Pat. Nos. 6,448,307, 6,258,876;6,207,729,5,973,035 and 5,952,105.

In some embodiments, the biomass material includes a carbohydrate thatis or includes a material having one or more β-1,4-linkages and having anumber average molecular weight between about 3,000 and 50,000. Such acarbohydrate is or includes cellulose (I), which is derived from(β-glucose 1) through condensation of β(1,4)-glycosidic bonds. Thislinkage contrasts itself with that for α(1,4)-glycosidic bonds presentin starch and other carbohydrates.

Starchy materials include starch itself, e.g., corn starch, wheatstarch, potato starch or rice starch, a derivative of starch, or amaterial that includes starch, such as an edible food product or a crop.For example, the starchy material can be arracacha, buckwheat, banana,barley, cassaya, kudzu, oca, sago, sorghum, regular household potatoes,sweet potato, taro, yams, or one or more beans, such as favas, lentilsor peas. Blends of any two or more starchy materials are also starchymaterials.

In some cases the biomass is a microbial material. Microbial sourcesinclude, but are not limited to, any naturally occurring or geneticallymodified microorganism or organism that contains or is capable ofproviding a source of carbohydrates (e.g., cellulose), for example,protists, e.g., animal protists (e.g., protozoa such as flagellates,amoeboids, ciliates, and sporozoa) and plant protists (e.g., algae suchalveolates, chlorarachniophytes, cryptomonads, euglenids, glaucophytes,haptophytes, red algae, stramenopiles, and viridaeplantae). Otherexamples include seaweed, plankton (e.g., macroplankton, mesoplankton,microplankton, nanoplankton, picoplankton, and femptoplankton),phytoplankton, bacteria (e.g., gram positive bacteria, gram negativebacteria, and extremophiles), yeast and/or mixtures of these. In someinstances, microbial biomass can be obtained from natural sources, e.g.,the ocean, lakes, bodies of water, e.g., salt water or fresh water, oron land. Alternatively or in addition, microbial biomass can be obtainedfrom culture systems, e.g., large scale dry and wet culture systems.

Saccharifying Agents

Suitable enzymes include cellobiases and cellulases capable of degradingbiomass.

Suitable cellobiases include a cellobiase from Aspergillus niger soldunder the tradename NOVOZYME 188™.

Cellulases are capable of degrading biomass, and may be of fungal orbacterial origin. Suitable enzymes include cellulases from the generaBacillus, Pseudomonas, Humicola, Fusarium, Thielavia, Acremonium,Chrysosporium and Trichoderma, and include species of Humicola,Coprinus, Thielavia, Fusarium, Myceliophthora, Acremonium,Cephalosporium, Scytalidium, Penicillium or Aspergillus (see, e.g., EP458162), especially those produced by a strain selected from the speciesHumicola insolens (reclassified as Scytalidium thermophilum, see, e.g.,U.S. Pat. No. 4,435,307), Coprinus cinereus, Fusarium oxysporum,Myceliophthora thermophila, Meripilus giganteus, Thielavia terrestris,Acremonium sp., Acremonium persicinum, Acremonium acremonium, Acremoniumbrachypenium, Acremonium dichromosporum, Acremonium obclavatum,Acremonium pinkertoniae, Acremonium roseogriseum, Acremoniumincoloratum, and Acremonium furatum; preferably from the speciesHumicola insolens DSM 1800, Fusarium oxysporum DSM 2672, Myceliophthorathermophila CBS117.65, Cephalosporium sp. RYM-202, Acremonium sp. CBS478.94, Acremonium sp. CBS 265.95, Acremonium persicinum CBS169.65,Acremonium acremonium AHU 9519, Cephalosporium sp. CBS 535.71,Acremonium brachypenium CBS 866.73, Acremonium dichromosporum CBS683.73, Acremonium obclavatum CBS 311.74, Acremonium pinkertoniaeCBS157.70, Acremonium roseogriseum CBS134.56, Acremonium incoloratumCBS146.62, and Acremonium furatum CBS 299.70H. Cellulolytic enzymes mayalso be obtained from Chrysosporium, preferably a strain ofChrysosporium lucknowense. Additionally, Trichoderma (particularlyTrichoderma viride, Trichoderma reesei, and Trichoderma koningii),alkalophilic Bacillus (see, for example, U.S. Pat. No. 3,844,890 and EP458162), and Streptomyces (see, e.g., EP 458162) may be used.

Enzyme complexes may be utilized, such as those available from Genencoreunder the tradename ACCELLERASE®, for example, Accellerase® 1500 enzymecomplex. Accellerase 1500 enzyme complex contains multiple enzymeactivities, mainly exoglucanase, endoglucanase (2200-2800 CMC U/g),hemi-cellulase, and beta-glucosidase (525-775 pNPG U/g), and has a pH of4.6 to 5.0. The endoglucanase activity of the enzyme complex isexpressed in carboxymethylcellulose activity units (CMC U), while thebeta-glucosidase activity is reported in pNP-glucoside activity units(pNPG-U). In one embodiment, a blend of Accellerase® 1500 enzyme complexand NOVOZYME™ 188 cellobiase is used.

In some implementations, the saccharifying agent comprises an acid,e.g., a mineral acid. When an acid is used, co-products may be generatedthat are toxic to microorganisms, in which case the process can furtherinclude removing such co-products. Removal may be performed using anactivated carbon, e.g., activated charcoal, or other suitabletechniques.

Fermentation Agents

The microorganism(s) used in fermentation can be natural microorganismsand/or engineered microorganisms. For example, the microorganism can bea bacterium, e.g., a cellulolytic bacterium, a fungus, e.g., a yeast, aplant or a protist, e.g., an algae, a protozoa or a fungus-like protist,e.g., a slime mold. When the organisms are compatible, mixtures oforganisms can be utilized.

Suitable fermenting microorganisms have the ability to convertcarbohydrates, such as glucose, xylose, arabinose, mannose, galactose,oligosaccharides or polysaccharides into fermentation products.Fermenting microorganisms include strains of the genus Sacchromyces spp.e.g., Sacchromyces cerevisiae (baker's yeast), Saccharomyces distaticus,Saccharomyces uvarum; the genus Kluyveromyces, e.g., speciesKluyveromyces marxianus, Kluyveromyces fragilis; the genus Candida,e.g., Candida pseudotropicalis, and Candida brassicae, Pichia stipitis(a relative of Candida shehatae, the genus Clavispora, e.g., speciesClavispora lusitaniae and Clavispora opuntiae, the genus Pachysolen,e.g., species Pachysolen tannophilus, the genus Bretannomyces, e.g.,species Bretannomyces clausenii (Philippidis, G. P., 1996, Cellulosebioconversion technology, in Handbook on Bioethanol: Production andUtilization, Wyman, C. E., ed., Taylor & Francis, Washington, D.C.,179-212).

Commercially available yeasts include, for example, Red Star®/LesaffreEthanol Red (available from Red Star/Lesaffre, USA), FALI® (availablefrom Fleischmann's Yeast, a division of Burns Philip Food Inc., USA),SUPERSTART® (available from Alltech, now Lalemand), GERT STRAND®(available from Gert Strand AB, Sweden) and FERMOL® (available from DSMSpecialties).

Bacteria may also be used in fermentation, e.g., Zymomonas mobilis andClostridium thermocellum (Philippidis, 1996, supra).

Additives

Antibiotics

While it is generally preferred to have a high sugar concentration inthe saccharified solution, lower concentrations may be used, in whichcase it may be desirable to add an antimicrobial additive, e.g., a broadspectrum antibiotic, in a low concentration, e.g., 50 to 150 ppm. Othersuitable antibiotics include amphotericin B, ampicillin,chloramphenicol, ciprofloxacin, gentamicin, hygromycin B, kanamycin,neomycin, penicillin, puromycin, streptomycin. Antibiotics will inhibitgrowth of microorganisms during transport and storage, and can be usedat appropriate concentrations, e.g., between 15 and 1000 ppm by weight,e.g., between 25 and 500 ppm, or between 50 and 150 ppm. If desired, anantibiotic can be included even if the sugar concentration is relativelyhigh.

Surfactants

The addition of surfactants can enhance the rate of saccharification.Examples of surfactants include non-ionic surfactants, such as a Tween®20 or Tween® 80 polyethylene glycol surfactants, ionic surfactants, oramphoteric surfactants. Other suitable surfactants include octylphenolethoxylates such as the TRITON™ X series nonionic surfactantscommercially available from Dow Chemical. A surfactant can also be addedto keep the sugar that is being produced in solution, particularly inhigh concentration solutions.

Saccharification Medium

In one embodiment, the medium has the following concentrations ofcomponents:

Yeast nitrogen base  1.7 g/L Urea 2.27 g/L Peptone 6.56 g/L Tween ® 80surfactant   10 g/L

Physical Treatment of Feedstock

In some implementations, the feedstock is physically treated prior tosaccharification and/or fermentation. Physical treatment processes caninclude one or more of any of those described herein, such as mechanicaltreatment, chemical treatment, irradiation, sonication, oxidation,pyrolysis or steam explosion. Treatment methods can be used incombinations of two, three, four, or even all of these technologies (inany order). When more than one treatment method is used, the methods canbe applied at the same time or at different times. Other processes thatchange a molecular structure of a biomass feedstock may also be used,alone or in combination with the processes disclosed herein.

Mechanical Treatments

In some cases, methods can include mechanically treating the biomassfeedstock. Mechanical treatments include, for example, cutting, milling,pressing, grinding, shearing and chopping. Milling may include, forexample, ball milling, hammer milling, rotor/stator dry or wet milling,or other types of milling. Other mechanical treatments include, e.g.,stone grinding, cracking, mechanical ripping or tearing, pin grinding orair attrition milling.

Mechanical treatment can be advantageous for “opening up,” “stressing,”breaking and shattering the cellulosic or lignocellulosic materials,making the cellulose of the materials more susceptible to chain scissionand/or reduction of crystallinity. The open materials can also be moresusceptible to oxidation when irradiated.

In some cases, the mechanical treatment may include an initialpreparation of the feedstock as received, e.g., size reduction ofmaterials, such as by cutting, grinding, shearing, pulverizing orchopping. For example, in some cases, loose feedstock (e.g., recycledpaper, starchy materials, or switchgrass) is prepared by shearing orshredding.

Alternatively, or in addition, the feedstock material can first bephysically treated by one or more of the other physical treatmentmethods, e.g., chemical treatment, radiation, sonication, oxidation,pyrolysis or steam explosion, and then mechanically treated. Thissequence can be advantageous since materials treated by one or more ofthe other treatments, e.g., irradiation or pyrolysis, tend to be morebrittle and, therefore, it may be easier to further change the molecularstructure of the material by mechanical treatment.

In some embodiments, the feedstock material is in the form of a fibrousmaterial, and mechanical treatment includes shearing to expose fibers ofthe fibrous material. Shearing can be performed, for example, using arotary knife cutter. Other methods of mechanically treating thefeedstock include, for example, milling or grinding. Milling may beperformed using, for example, a hammer mill, ball mill, colloid mill,conical or cone mill, disk mill, edge mill, Wiley mill or grist mill.Grinding may be performed using, for example, a stone grinder, pingrinder, coffee grinder, or burr grinder. Grinding may be provided, forexample, by a reciprocating pin or other element, as is the case in apin mill. Other mechanical treatment methods include mechanical rippingor tearing, other methods that apply pressure to the material, and airattrition milling. Suitable mechanical treatments further include anyother technique that changes the molecular structure of the feedstock.

If desired, the mechanically treated material can be passed through ascreen, e.g., having an average opening size of 1.59 mm or less ( 1/16inch, 0.0625 inch). In some embodiments, shearing, or other mechanicaltreatment, and screening are performed concurrently. For example, arotary knife cutter can be used to concurrently shear and screen thefeedstock. The feedstock is sheared between stationary blades androtating blades to provide a sheared material that passes through ascreen, and is captured in a bin.

The cellulosic or lignocellulosic material can be mechanically treatedin a dry state (e.g., having little or no free water on its surface), ahydrated state (e.g., having up to ten percent by weight absorbedwater), or in a wet state, e.g., having between about 10 percent andabout 75 percent by weight water. The fiber source can even bemechanically treated while partially or fully submerged under a liquid,such as water, ethanol or isopropanol.

The cellulosic or lignocellulosic material can also be mechanicallytreated under a gas (such as a stream or atmosphere of gas other thanair), e.g., oxygen or nitrogen, or steam.

If desired, lignin can be removed from any of the fibrous materials thatinclude lignin. Also, to aid in the breakdown of the materials thatinclude cellulose, the material can be treated prior to or duringmechanical treatment or irradiation with heat, a chemical (e.g., mineralacid, base or a strong oxidizer such as sodium hypochlorite) and/or anenzyme. For example, grinding can be performed in the presence of anacid.

Mechanical treatment systems can be configured to produce streams withspecific morphology characteristics such as, for example, surface area,porosity, bulk density, and, in the case of fibrous feedstocks, fibercharacteristics such as length-to-width ratio.

In some embodiments, a BET surface area of the mechanically treatedmaterial is greater than 0.1 m²/g, e.g., greater than 0.25 m²/g, greaterthan 0.5 m²/g, greater than 1.0 m²/g, greater than 1.5 m²/g, greaterthan 1.75 m²/g, greater than 5.0 m²/g, greater than 10 m²/g, greaterthan 25 m²/g, greater than 35 m²/g, greater than 50 m²/g, greater than60 m²/g, greater than 75 m²/g, greater than 100 m²/g, greater than 150m²/g, greater than 200 m²/g, or even greater than 250 m²/g.

A porosity of the mechanically treated material can be, e.g., greaterthan 20 percent, greater than 25 percent, greater than 35 percent,greater than 50 percent, greater than 60 percent, greater than 70percent, greater than 80 percent, greater than 85 percent, greater than90 percent, greater than 92 percent, greater than 94 percent, greaterthan 95 percent, greater than 97.5 percent, greater than 99 percent, oreven greater than 99.5 percent.

In some embodiments, after mechanical treatment the material has a bulkdensity of less than 0.25 g/cm³, e.g., 0.20 g/cm³, 0.15 g/cm³, 0.10g/cm³, 0.05 g/cm³ or less, e.g., 0.025 g/cm³. Bulk density is determinedusing ASTM D1895B. Briefly, the method involves filling a measuringcylinder of known volume with a sample and obtaining a weight of thesample. The bulk density is calculated by dividing the weight of thesample in grams by the known volume of the cylinder in cubiccentimeters.

If the feedstock is a fibrous material the fibers of the mechanicallytreated material can have a relatively large average length-to-diameterratio (e.g., greater than 20-to-1), even if they have been sheared morethan once. In addition, the fibers of the fibrous materials describedherein may have a relatively narrow length and/or length-to-diameterratio distribution.

As used herein, average fiber widths (e.g., diameters) are thosedetermined optically by randomly selecting approximately 5,000 fibers.Average fiber lengths are corrected length-weighted lengths. BET(Brunauer, Emmet and Teller) surface areas are multi-point surfaceareas, and porosities are those determined by mercury porosimetry.

If the feedstock is a fibrous material the average length-to-diameterratio of fibers of the mechanically treated material can be, e.g.,greater than 8/1, e.g., greater than 10/1, greater than 15/1, greaterthan 20/1, greater than 25/1, or greater than 50/1. An average fiberlength of the mechanically treated material can be, e.g., between about0.5 mm and 2.5 mm, e.g., between about 0.75 mm and 1.0 mm, and anaverage width (e.g., diameter) of the second fibrous material 14 can be,e.g., between about 5 μm and 50 μm, e.g., between about 10 μm and 30 μm.

In some embodiments, if the feedstock is a fibrous material the standarddeviation of the fiber length of the mechanically treated material canbe less than 60 percent of an average fiber length of the mechanicallytreated material, e.g., less than 50 percent of the average length, lessthan 40 percent of the average length, less than 25 percent of theaverage length, less than 10 percent of the average length, less than 5percent of the average length, or even less than 1 percent of theaverage length.

In some situations, it can be desirable to prepare a low bulk densitymaterial, densify the material (e.g., to make it easier and less costlyto transport to another site), and then revert the material to a lowerbulk density state. Densified materials can be processed by any of themethods described herein, or any material processed by any of themethods described herein can be subsequently densified, e.g., asdisclosed in U.S. Ser. No. 12/429,045 and WO 2008/073186, the fulldisclosures of which are incorporated herein by reference.

Radiation Treatment

One or more radiation processing sequences can be used to process thefeedstock, and to provide a structurally modified material whichfunctions as input to further processing steps and/or sequences.Irradiation can, for example, reduce the molecular weight and/orcrystallinity of feedstock. Radiation can also sterilize the materials,or any media needed to bioprocess the material.

In some embodiments, energy deposited in a material that releases anelectron from its atomic orbital is used to irradiate the materials. Theradiation may be provided by (1) heavy charged particles, such as alphaparticles or protons, (2) electrons, produced, for example, in betadecay or electron beam accelerators, or (3) electromagnetic radiation,for example, gamma rays, x rays, or ultraviolet rays. In one approach,radiation produced by radioactive substances can be used to irradiatethe feedstock. In another approach, electromagnetic radiation (e.g.,produced using electron beam emitters) can be used to irradiate thefeedstock. In some embodiments, any combination in any order orconcurrently of (1) through (3) may be utilized. The doses applieddepend on the desired effect and the particular feedstock.

In some instances when chain scission is desirable and/or polymer chainfunctionalization is desirable, particles heavier than electrons, suchas protons, helium nuclei, argon ions, silicon ions, neon ions, carbonions, phoshorus ions, oxygen ions or nitrogen ions can be utilized. Whenring-opening chain scission is desired, positively charged particles canbe utilized for their Lewis acid properties for enhanced ring-openingchain scission. For example, when maximum oxidation is desired, oxygenions can be utilized, and when maximum nitration is desired, nitrogenions can be utilized. The use of heavy particles and positively chargedparticles is described in U.S. Ser. No. 12/417,699, the full disclosureof which is incorporated herein by reference.

In one method, a first material that is or includes cellulose having afirst number average molecular weight (M_(N1)) is irradiated, e.g., bytreatment with ionizing radiation (e.g., in the form of gamma radiation,X-ray radiation, 100 nm to 280 nm ultraviolet (UV) light, a beam ofelectrons or other charged particles) to provide a second material thatincludes cellulose having a second number average molecular weight(M_(N2)) lower than the first number average molecular weight. Thesecond material (or the first and second material) can be combined witha microorganism (with or without enzyme treatment) that can utilize thesecond and/or first material or its constituent sugars or lignin toproduce an intermediate or product, such as those described herein.

Since the second material includes cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable and/or soluble, e.g., in a solution containing amicroorganism and/or an enzyme. These properties make the secondmaterial easier to process and more susceptible to chemical, enzymaticand/or biological attack relative to the first material, which cangreatly improve the production rate and/or production level of a desiredproduct, e.g., ethanol.

In some embodiments, the second number average molecular weight (M_(N2))is lower than the first number average molecular weight (M_(N1)) by morethan about 10 percent, e.g., more than about 15, 20, 25, 30, 35, 40, 50percent, 60 percent, or even more than about 75 percent.

In some instances, the second material includes cellulose that has acrystallinity (C₂) that is lower than the crystallinity (C₁) of thecellulose of the first material. For example, (C₂) can be lower than(C₁) by more than about 10 percent, e.g., more than about 15, 20, 25,30, 35, 40, or even more than about 50 percent. In some embodiments, thestarting crystallinity index (prior to irradiation) is from about 40 toabout 87.5 percent, e.g., from about 50 to about 75 percent or fromabout 60 to about 70 percent, and the crystallinity index afterirradiation is from about 10 to about 50 percent, e.g., from about 15 toabout 45 percent or from about 20 to about 40 percent. However, in someembodiments, e.g., after extensive irradiation, it is possible to have acrystallinity index of lower than 5 percent. In some embodiments, thematerial after irradiation is substantially amorphous.

In some embodiments, the starting number average molecular weight (priorto irradiation) is from about 200,000 to about 3,200,000, e.g., fromabout 250,000 to about 1,000,000 or from about 250,000 to about 700,000,and the number average molecular weight after irradiation is from about50,000 to about 200,000, e.g., from about 60,000 to about 150,000 orfrom about 70,000 to about 125,000. However, in some embodiments, e.g.,after extensive irradiation, it is possible to have a number averagemolecular weight of less than about 10,000 or even less than about5,000.

In some embodiments, the second material can have a level of oxidation(O₂) that is higher than the level of oxidation (O₁) of the firstmaterial. A higher level of oxidation of the material can aid in itsdispersability, swellability and/or solubility, further enhancing thematerial's susceptibility to chemical, enzymatic or biological attack.In some embodiments, to increase the level of the oxidation of thesecond material relative to the first material, the irradiation isperformed under an oxidizing environment, e.g., under a blanket of airor oxygen, producing a second material that is more oxidized than thefirst material. For example, the second material can have more hydroxylgroups, aldehyde groups, ketone groups, ester groups or carboxylic acidgroups, which can increase its hydrophilicity.

Ionizing Radiation

Each form of radiation ionizes the carbon-containing material viaparticular interactions, as determined by the energy of the radiation.Heavy charged particles primarily ionize matter via Coulomb scattering;furthermore, these interactions produce energetic electrons that mayfurther ionize matter. Alpha particles are identical to the nucleus of ahelium atom and are produced by the alpha decay of various radioactivenuclei, such as isotopes of bismuth, polonium, astatine, radon,francium, radium, several actinides, such as actinium, thorium, uranium,neptunium, curium, californium, americium, and plutonium.

When particles are utilized, they can be neutral (uncharged), positivelycharged or negatively charged. When charged, the charged particles canbear a single positive or negative charge, or multiple charges, e.g.,one, two, three or even four or more charges. In instances in whichchain scission is desired, positively charged particles may bedesirable, in part due to their acidic nature. When particles areutilized, the particles can have the mass of a resting electron, orgreater, e.g., 500, 1000, 1500, 2000, 10,000 or even 100,000 times themass of a resting electron. For example, the particles can have a massof from about 1 atomic unit to about 150 atomic units, e.g., from about1 atomic unit to about 50 atomic units, or from about 1 to about 25,e.g., 1, 2, 3, 4, 5, 10, 12 or 15 amu. Accelerators used to acceleratethe particles can be electrostatic DC, electrodynamic DC, RF linear,magnetic induction linear or continuous wave. For to example, cyclotrontype accelerators are available from IBA, Belgium, such as theRhodotron® system, while DC type accelerators are available from RDI,now IBA Industrial, such as the Dynamitron®. Ions and ion acceleratorsare discussed in Introductory Nuclear Physics, Kenneth S. Krane, JohnWiley & Sons, Inc. (1988), Krsto Prelec, FIZIKA B 6 (1997) 4, 177-206,Chu, William T., “Overview of Light-Ion Beam Therapy” Columbus-Ohio,ICRU-IAEA Meeting, 18-20 Mar. 2006, Iwata, Y. et al.,“Alternating-Phase-Focused 1H-DTL for Heavy-Ion Medical Accelerators”Proceedings of EPAC 2006, Edinburgh, Scotland and Leaner, C. M. et al.,“Status of the Superconducting ECR Ion Source Venus” Proceedings of EPAC2000, Vienna, Austria.

Gamma radiation has the advantage of a significant penetration depthinto a variety of materials. Sources of gamma rays include radioactivenuclei, such as isotopes of cobalt, calcium, technicium, chromium,gallium, indium, iodine, iron, krypton, samarium, selenium, sodium,thalium, and xenon.

Sources of x rays include electron beam collision with metal targets,such as tungsten or molybdenum or alloys, or compact light sources, suchas those produced commercially by Lyncean.

Sources for ultraviolet radiation include deuterium or cadmium lamps.

Sources for infrared radiation include sapphire, zinc, or selenidewindow ceramic lamps.

Sources for microwaves include klystrons, Slevin type RF sources, oratom beam sources that employ hydrogen, oxygen, or nitrogen gases.

In some embodiments, a beam of electrons is used as the radiationsource. A beam of electrons has the advantages of high dose rates (e.g.,1, 5, or even 10 Mrad per second), high throughput, less containment,and less confinement equipment. Electrons can also be more efficient atcausing chain scission. In addition, electrons having energies of 4-10MeV can have a penetration depth of 5 to 30 mm or more, such as 40 mm.

Electron beams can be generated, e.g., by electrostatic generators,cascade generators, transformer generators, low energy accelerators witha scanning system, low energy accelerators with a linear cathode, linearaccelerators, and pulsed accelerators. Electrons as an ionizingradiation source can be useful, e.g., for relatively thin sections ofmaterial, e.g., less than 0.5 inch, e.g., less than 0.4 inch, 0.3 inch,0.2 inch, or less than 0.1 inch. In some embodiments, the energy of eachelectron of the electron beam is from about 0.3 MeV to about 2.0 MeV(million electron volts), e.g., from about 0.5 MeV to about 1.5 MeV, orfrom about 0.7 MeV to about 1.25 MeV.

Electron beam irradiation devices may be procured commercially from IonBeam Applications, Louvain-la-Neuve, Belgium or the Titan Corporation,San Diego, Calif. Typical electron energies can be 1 MeV, 2 MeV, 4.5MeV, 7.5 MeV, or 10 MeV. Typical electron beam irradiation device powercan be 1 kW, 5 kW, 10 kW, 20 kW, 50 kW, 100 kW, 250 kW, or 500 kW. Thelevel of depolymerization of the feedstock depends on the electronenergy used and the dose applied, while exposure time depends on thepower and dose. Typical doses may take values of 1 kGy, 5 kGy, 10 kGy,20 kGy, 50 kGy, 100 kGy, or 200 kGy.

Ion Particle Beams

Particles heavier than electrons can be utilized to irradiate materials,such as carbohydrates or materials that include carbohydrates, e.g.,cellulosic materials, lignocellulosic materials, starchy materials, ormixtures of any of these and others described herein. For example,protons, helium nuclei, argon ions, silicon ions, neon ions carbon ions,phoshorus ions, oxygen ions or nitrogen ions can be utilized. In someembodiments, particles heavier than electrons can induce higher amountsof chain scission (relative to lighter particles). In some instances,positively charged particles can induce higher amounts of chain scissionthan negatively charged particles due to their acidity.

Heavier particle beams can be generated, e.g., using linear acceleratorsor cyclotrons. In some embodiments, the energy of each particle of thebeam is from about 1.0 MeV/atomic unit to about 6,000 MeV/atomic unit,e.g., from about 3 MeV/atomic unit to about 4,800 MeV/atomic unit, orfrom about 10 MeV/atomic unit to about 1,000 MeV/atomic unit.

In certain embodiments, ion beams used to irradiate carbon-containingmaterials, e.g., biomass materials, can include more than one type ofion. For example, ion beams can include mixtures of two or more (e.g.,three, four or more) different types of ions. Exemplary mixtures caninclude carbon ions and protons, carbon ions and oxygen ions, nitrogenions and protons, and iron ions and protons. More generally, mixtures ofany of the ions discussed above (or any other ions) can be used to formirradiating ion beams. In particular, mixtures of relatively light andrelatively heavier ions can be used in a single ion beam.

In some embodiments, ion beams for irradiating materials includepositively-charged ions. The positively charged ions can include, forexample, positively charged hydrogen ions (e.g., protons), noble gasions (e.g., helium, neon, argon), carbon ions, nitrogen ions, oxygenions, silicon atoms, phosphorus ions, and metal ions such as sodiumions, calcium ions, and/or iron ions. Without wishing to be bound by anytheory, it is believed that such positively-charged ions behavechemically as Lewis acid moieties when exposed to materials, initiatingand sustaining cationic ring-opening chain scission reactions in anoxidative environment.

In certain embodiments, ion beams for irradiating materials includenegatively-charged ions. Negatively charged ions can include, forexample, negatively charged hydrogen ions (e.g., hydride ions), andnegatively charged ions of various relatively electronegative nuclei(e.g., oxygen ions, nitrogen ions, carbon ions, silicon ions, andphosphorus ions). Without wishing to be bound by any theory, it isbelieved that such negatively-charged ions behave chemically as Lewisbase moieties when exposed to materials, causing anionic ring-openingchain scission reactions in a reducing environment.

In some embodiments, beams for irradiating materials can include neutralatoms. For example, any one or more of hydrogen atoms, helium atoms,carbon atoms, nitrogen atoms, oxygen atoms, neon atoms, silicon atoms,phosphorus atoms, argon atoms, and iron atoms can be included in beamsthat are used for irradiation of biomass materials. In general, mixturesof any two or more of the above types of atoms (e.g., three or more,four or more, or even more) can be present in the beams.

In certain embodiments, ion beams used to irradiate materials includesingly-charged ions such as one or more of H⁺, H⁻, He⁺, Ne⁺, Ar⁺, C⁺,C⁻, O⁺, N⁺, N⁻, Si⁺, Si⁻, P⁺, P⁻, Na⁺, Ca⁺, and Fe⁺. In someembodiments, ion beams can include multiply-charged ions such as one ormore of C²⁺, C³⁺, C⁴⁺, N³⁺, N⁵⁺, N³⁻, O²⁺, O²⁻, O₂ ²⁻, Si²⁺, Si⁴⁺, Si²⁻,and Si⁴⁻. In general, the ion beams can also include more complexpolynuclear ions that bear multiple positive or negative charges. Incertain embodiments, by virtue of the structure of the polynuclear ion,the positive or negative charges can be effectively distributed oversubstantially the entire structure of the ions. In some embodiments, thepositive or negative charges can be somewhat localized over portions ofthe structure of the ions.

Electromagnetic Radiation

In embodiments in which the irradiating is performed withelectromagnetic radiation, the electromagnetic radiation can have, e.g.,energy per photon (in electron volts) of greater than 10² eV, e.g.,greater than 10³, 10⁴, 10⁵, 10⁶, or even greater than 10⁷ eV. In someembodiments, the electromagnetic radiation has energy per photon ofbetween 10⁴ and 10⁷, e.g., between 10⁵ and 10⁶ eV. The electromagneticradiation can have a frequency of, e.g., greater than 10¹⁶ hz, greaterthan 10¹⁷ hz, 10¹⁸, 10¹⁹, 10²⁰, or even greater than 10²¹ hz. In someembodiments, the electromagnetic radiation has a frequency of between10¹⁸ and 10²² hz, e.g., between 10¹⁹ to 10²¹ hz.

Quenching and Controlled Functionalization

After treatment with ionizing radiation, any of the materials ormixtures described herein may become ionized; that is, the treatedmaterial may include radicals at levels that are detectable with anelectron spin resonance spectrometer. If ionized biomass remains in theatmosphere, it will be oxidized, such as to an extent that carboxylicacid groups are generated by reacting with the atmospheric oxygen. Insome instances with some materials, such oxidation is desired because itcan aid in the further breakdown in molecular weight of thecarbohydrate-containing biomass, and the oxidation groups, e.g.,carboxylic acid groups can be helpful for solubility and microorganismutilization in some instances. However, since the radicals can “live”for some time after irradiation, e.g., longer than 1 day, 5 days, 30days, 3 months, 6 months or even longer than 1 year, material propertiescan continue to change over time, which in some instances, can beundesirable. Thus, it may be desirable to quench the ionized material.

After ionization, any biomass material that has been ionized can bequenched to reduce the level of radicals in the ionized biomass, e.g.,such that the radicals are no longer detectable with the electron spinresonance spectrometer. For example, the radicals can be quenched by theapplication of a sufficient pressure to the biomass and/or by utilizinga fluid in contact with the ionized biomass, such as a gas or liquid,that reacts with (quenches) the radicals. Using a gas or liquid to atleast aid in the quenching of the radicals can be used to functionalizethe ionized biomass with a desired amount and kind of functional groups,such as carboxylic acid groups, enol groups, aldehyde groups, nitrogroups, nitrile groups, amino groups, alkyl amino groups, alkyl groups,chloroalkyl groups or chlorofluoroalkyl groups.

In some instances, such quenching can improve the stability of some ofthe ionized biomass materials. For example, quenching can improve theresistance of the biomass to oxidation. Functionalization by quenchingcan also improve the solubility of any biomass described herein, canimprove its thermal stability, and can improve material utilization byvarious microorganisms. For example, the functional groups imparted tothe biomass material by the quenching can act as receptor sites forattachment by microorganisms, e.g., to enhance cellulose hydrolysis byvarious microorganisms.

In some embodiments, quenching includes an application of pressure tothe biomass, such as by mechanically deforming the biomass, e.g.,directly mechanically compressing the biomass in one, two, or threedimensions, or applying pressure to a fluid in which the biomass isimmersed, e.g., isostatic pressing. In such instances, the deformationof the material itself brings radicals, which are often trapped incrystalline domains, in close enough proximity so that the radicals canrecombine, or react with another group. In some instances, the pressureis applied together with the application of heat, such as a sufficientquantity of heat to elevate the temperature of the biomass to above amelting point or softening point of a component of the biomass, such aslignin, cellulose or hemicellulose. Heat can improve molecular mobilityin the material, which can aid in the quenching of the radicals. Whenpressure is utilized to quench, the pressure can be greater than about1000 psi, such as greater than about 1250 psi, 1450 psi, 3625 psi, 5075psi, 7250 psi, 10000 psi or even greater than 15000 psi. In someembodiments, quenching includes contacting the biomass with a fluid,such as a liquid or gas, e.g., a gas capable of reacting with theradicals, such as acetylene or a mixture of acetylene in nitrogen,ethylene, chlorinated ethylenes or chlorofluoroethylenes, propylene ormixtures of these gases. In other particular embodiments, quenchingincludes contacting the biomass with a liquid, e.g., a liquid solublein, or at least capable of penetrating into the biomass and reactingwith the radicals, such as a diene, such as 1,5-cyclooctadiene. In somespecific embodiments, quenching includes contacting the biomass with anantioxidant, such as Vitamin E. If desired, the biomass feedstock caninclude an antioxidant dispersed therein, and the quenching can comefrom contacting the antioxidant dispersed in the biomass feedstock withthe radicals.

Functionalization can be enhanced by utilizing heavy charged ions, suchas any of the heavier ions described herein. For example, if it isdesired to enhance oxidation, charged oxygen ions can be utilized forthe irradiation. If nitrogen functional groups are desired, nitrogenions or anions that include nitrogen can be utilized. Likewise, ifsulfur or phosphorus groups are desired, sulfur or phosphorus ions canbe used in the irradiation.

Doses

In some instances, the irradiation is performed at a dosage rate ofgreater than about 0.25 Mrad per second, e.g., greater than about 0.5,0.75, 1.0, 1.5, 2.0, or even greater than about 2.5 Mrad per second. Insome embodiments, the irradiating is performed at a dose rate of between5.0 and 1500.0 kilorads/hour, e.g., between 10.0 and 750.0 kilorads/houror between 50.0 and 350.0 kilorads/hour.

In some embodiments, the irradiating (with any radiation source or acombination of sources) is performed until the material receives a doseof at least 0.1 Mrad, at least 0.25 Mrad, e.g., at least 1.0 Mrad, atleast 2.5 Mrad, at least 5.0 Mrad, at least 10.0 Mrad, at least 60 Mrador at least 100 Mrad. In some embodiments, the irradiating is performeduntil the material receives a dose of from about 0.1 Mrad to about 500Mrad, from about 0.5 Mrad to about 200 Mrad, from about 1 Mrad to about100 Mrad, or from about 5 Mrad to about 60 Mrad. In some embodiments, arelatively low dose of radiation is applied, e.g., less than 60 Mrad.

Sonication

Sonication can reduce the molecular weight and/or crystallinity ofmaterials, such as one or more of any of the materials described herein,e.g., one or more carbohydrate sources, such as cellulosic orlignocellulosic materials, or starchy materials. Sonication can also beused to sterilize the materials. As discussed above with regard toradiation, the process parameters used for sonication can be varieddepending on various factors, e.g., depending on the lignin content ofthe feedstock. For example, feedstocks with higher lignin levelsgenerally require a higher residence time and/or energy level, resultingin a higher total energy delivered to the feedstock.

In one method, a first material that includes cellulose having a firstnumber average molecular weight (M_(N1)) is dispersed in a medium, suchas water, and sonicated and/or otherwise cavitated, to provide a secondmaterial that includes cellulose having a second number averagemolecular weight (M_(N2)) lower than the first number average molecularweight. The second material (or the first and second material in certainembodiments) can be combined with a microorganism (with or withoutenzyme treatment) that can utilize the second and/or first material toproduce an intermediate or product.

Since the second material includes cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable, and/or soluble, e.g., in a solution containing amicroorganism.

In some embodiments, the second number average, molecular weight(M_(N2)) is lower than the first number average molecular weight(M_(N1)) by more than about 10 percent, e.g., more than about 15, 20,25, 30, 35, 40, 50 percent, 60 percent, or even more than about 75percent.

In some instances, the second material includes cellulose that has acrystallinity (C₂) that is lower than the crystallinity (C₁) of thecellulose of the first material. For example, (C₂) can be lower than(C₁) by more than about 10 percent, e.g., more than about 15, 20, 25,30, 35, 40, or even more than about 50 percent.

In some embodiments, the starting crystallinity index (prior tosonication) is from about 40 to about 87.5 percent, e.g., from about 50to about 75 percent or from about 60 to about 70 percent, and thecrystallinity index after sonication is from about 10 to about 50percent, e.g., from about 15 to about 45 percent or from about 20 toabout 40 percent. However, in certain embodiments, e.g., after extensivesonication, it is possible to have a crystallinity index of lower than 5percent. In some embodiments, the material after sonication issubstantially amorphous.

In some embodiments, the starting number average molecular weight (priorto sonication) is from about 200,000 to about 3,200,000, e.g., fromabout 250,000 to about 1,000,000 or from about 250,000 to about 700,000,and the number average molecular weight after sonication is from about50,000 to about 200,000, e.g., from about 60,000 to about 150,000 orfrom about 70,000 to about 125,000. However, in some embodiments, e.g.,after extensive sonication, it is possible to have a number averagemolecular weight of less than about 10,000 or even less than about5,000.In some embodiments, the second material can have a level of oxidation(O₂) that is higher than the level of oxidation (O₁) of the firstmaterial. A higher level of oxidation of the material can aid in itsdispersability, swellability and/or solubility, further enhancing thematerial's susceptibility to chemical, enzymatic or microbial attack. Insome embodiments, to increase the level of the oxidation of the secondmaterial relative to the first material, the sonication is performed inan oxidizing medium, producing a second material that is more oxidizedthan the first material. For example, the second material can have morehydroxyl groups, aldehyde groups, ketone groups, ester groups orcarboxylic acid groups, which can increase its hydrophilicity.

In some embodiments, the sonication medium is an aqueous medium. Ifdesired, the medium can include an oxidant, such as a peroxide (e.g.,hydrogen peroxide), a dispersing agent and/or a buffer. Examples ofdispersing agents include ionic dispersing agents, e.g., sodium laurylsulfate, and non-ionic dispersing agents, e.g., poly(ethylene glycol).

In other embodiments, the sonication medium is non-aqueous. For example,the sonication can be performed in a hydrocarbon, e.g., toluene orheptane, an ether, e.g., diethyl ether or tetrahydrofuran, or even in aliquefied gas such as argon, xenon, or nitrogen.

Pyrolysis

One or more pyrolysis processing sequences can be used to processcarbon-containing materials from a wide variety of different sources toextract useful substances from the materials, and to provide partiallydegraded materials which function as input to further processing stepsand/or sequences. Pyrolysis can also be used to sterilize the materials.Pyrolysis conditions can be varied depending on the characteristics ofthe feedstock and/or other factors. For example, feedstocks with higherlignin levels may require a higher temperature, longer residence time,and/or introduction of higher levels of oxygen during pyrolysis.

In one example, a first material that includes cellulose having a firstnumber average molecular weight (M_(N1)) is pyrolyzed, e.g., by heatingthe first material in a tube furnace (in the presence or absence ofoxygen), to provide a second material that includes cellulose having asecond number average molecular weight (M_(N2)) lower than the firstnumber average molecular weight.

Since the second material includes cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable and/or soluble, e.g., in a solution containing amicroorganism.

In some embodiments, the second number average molecular weight (M_(N2))is lower than the first number average molecular weight (MO by more thanabout 10 percent, e.g., more than about 15, 20, 25, 30, 35, 40, 50percent, 60 percent, or even more than about 75 percent.

In some instances, the second material includes cellulose that has acrystallinity (C₂) that is lower than the crystallinity (C₁) of thecellulose of the first material. For example, (C₂) can be lower than(C₁) by more than about 10 percent, e.g., more than about 15, 20, 25,30, 35, 40, or even more than about 50 percent.

In some embodiments, the starting crystallinity (prior to pyrolysis) isfrom about 40 to about 87.5 percent, e.g., from about 50 to about 75percent or from about 60 to about 70 percent, and the crystallinityindex after pyrolysis is from about 10 to about 50 percent, e.g., fromabout 15 to about 45 percent or from about 20 to about 40 percent.However, in certain embodiments, e.g., after extensive pyrolysis, it ispossible to have a crystallinity index of lower than 5 percent. In someembodiments, the material after pyrolysis is substantially amorphous.

In some embodiments, the starting number average molecular weight (priorto pyrolysis) is from about 200,000 to about 3,200,000, e.g., from about250,000 to about 1,000,000 or from about 250,000 to about 700,000, andthe number average molecular weight after pyrolysis is from about 50,000to about 200,000, e.g., from about 60,000 to about 150,000 or from about70,000 to about 125,000. However, in some embodiments, e.g., afterextensive pyrolysis, it is possible to have a number average molecularweight of less than about 10,000 or even less than about 5,000.

In some embodiments, the second material can have a level of oxidation(O₂) that is higher than the level of oxidation (O₁) of the firstmaterial. A higher level of oxidation of the material can aid in itsdispersability, swellability and/or solubility, further enhancing thesusceptibility of the material to chemical, enzymatic or microbialattack. In some embodiments, to increase the level of the oxidation ofthe second material relative to the first material, the pyrolysis isperformed in an oxidizing environment, producing a second material thatis more oxidized than the first material. For example, the secondmaterial can have more hydroxyl groups, aldehyde groups, ketone groups,ester groups or carboxylic acid groups, than the first material, therebyincreasing the hydrophilicity of the material.

In some embodiments, the pyrolysis of the materials is continuous. Inother embodiments, the material is pyrolyzed for a pre-determined time,and then allowed to cool for a second pre-determined time beforepyrolyzing again.

Oxidation

One or more oxidative processing sequences can be used to processcarbon-containing materials from a wide variety of different sources toextract useful substances from the materials, and to provide partiallydegraded and/or altered material which functions as input to furtherprocessing steps and/or sequences. The oxidation conditions can bevaried, e.g., depending on the lignin content of the feedstock, with ahigher degree of oxidation generally being desired for higher lignincontent feedstocks.

In one method, a first material that includes cellulose having a firstnumber average molecular weight (M_(N1)) and having a first oxygencontent (O₁) is oxidized, e.g., by heating the first material in astream of air or oxygen-enriched air, to provide a second material thatincludes cellulose having a second number average molecular weight(M_(N2)) and having a second oxygen content (O₂) higher than the firstoxygen content (O₁).

The second number average molecular weight of the second material isgenerally lower than the first number average molecular weight of thefirst material. For example, the molecular weight may be reduced to thesame extent as discussed above with respect to the other physicaltreatments. The crystallinity of the second material may also be reducedto the same extent as discussed above with respect to the other physicaltreatments.

In some embodiments, the second oxygen content is at least about fivepercent higher than the first oxygen content, e.g., 7.5 percent higher,10.0 percent higher, 12.5 percent higher, 15.0 percent higher or 17.5percent higher. In some preferred embodiments, the second oxygen contentis at least about 20.0 percent higher than the first oxygen content ofthe first material. Oxygen content is measured by elemental analysis bypyrolyzing a sample in a furnace operating at 1300° C. or higher. Asuitable elemental analyzer is the LECO CHNS-932 analyzer with a VTF-900high temperature pyrolysis furnace.

Generally, oxidation of a material occurs in an oxidizing environment.For example, the oxidation can be effected or aided by pyrolysis in anoxidizing environment, such as in air or argon enriched in air. To aidin the oxidation, various chemical agents, such as oxidants, acids orbases can be added to the material prior to or during oxidation. Forexample, a peroxide (e.g., benzoyl peroxide) can be added prior tooxidation.

Some oxidative methods of reducing recalcitrance in a biomass feedstockemploy Fenton-type chemistry. Such methods are disclosed, for example,in U.S. Ser. No. 12/639,289, the complete disclosure of which isincorporated herein by reference.

Exemplary oxidants include peroxides, such as hydrogen peroxide andbenzoyl peroxide, persulfates, such as ammonium persulfate, activatedforms of oxygen, such as ozone, permanganates, such as potassiumpermanganate, perchlorates, such as sodium perchlorate, andhypochlorites, such as sodium hypochlorite (household bleach).

In some situations, pH is maintained at or below about 5.5 duringcontact, such as between 1 and 5, between 2 and 5, between 2.5 and 5 orbetween about 3 and 5. Oxidation conditions can also include a contactperiod of between 2 and 12 hours, e.g., between 4 and 10 hours orbetween 5 and 8 hours. In some instances, temperature is maintained ator below 300° C., e.g., at or below 250, 200, 150, 100 or 50° C. In someinstances, the temperature remains substantially ambient, e.g., at orabout 20-25° C.

In some embodiments, the one or more oxidants are applied as a gas, suchas by generating ozone in-situ by irradiating the material through airwith a beam of particles, such as electrons.

In some embodiments, the mixture further includes one or morehydroquinones, such as 2,5-dimethoxyhydroquinone (DMHQ) and/or one ormore benzoquinones, such as 2,5-dimethoxy-1,4-benzoquinone (DMBQ), whichcan aid in electron transfer reactions.

In some embodiments, the one or more oxidants areelectrochemically-generated in-situ. For example, hydrogen peroxideand/or ozone can be electro-chemically produced within a contact orreaction vessel.

Other Processes to Solubilize, Reduce Recalcitrance or to Functionalize

Any of the processes of this paragraph can be used alone without any ofthe processes described herein, or in combination with any of theprocesses described herein (in any order): steam explosion, chemicaltreatment (e.g., acid treatment (including concentrated and dilute acidtreatment with mineral acids, such as sulfuric acid, hydrochloric acidand organic acids, such as trifluoroacetic acid) and/or base treatment(e.g., treatment with lime or sodium hydroxide)), UV treatment, screwextrusion treatment (see, e.g., U.S. Patent Application Ser. No.61/115,398, filed Nov. 17, 2008, solvent treatment (e.g., treatment withionic liquids) and freeze milling (see, e.g., U.S. Ser. No. 12/502,629).

Production of Fuels, Acids, Esters and/or Other Products

After one or more of the processing steps discussed above have beenperformed on the biomass, the complex carbohydrates contained in thecellulose and hemicellulose fractions can be processed into fermentablesugars using a saccharification process, as discussed above.

After the resulting sugar solution has been transported to amanufacturing facility, the sugars can be converted into a variety ofproducts, such as alcohols, e.g., ethanol, or organic acids. The productobtained depends upon the microorganism utilized and the conditionsunder which the bioprocessing occurs. These steps can be performed, forexample, utilizing the existing equipment of the corn-based ethanolmanufacturing facility.

The mixing processes and equipment discussed herein may also be usedduring bioprocessing, if desired. Advantageously, the mixing systemsdescribed herein do not impart high shear to the liquid, and do notsignificantly raise the overall temperature of the liquid. As a result,the microorganisms used in bioprocessing are maintained in a viablecondition throughout the process. Mixing may enhance the reaction rateand improve the efficiency of the process.

Generally, fermentation utilizes various microorganisms. The sugarsolution produced by saccharification of lignocellulosic materials willgenerally contain xylose as well as glucose. It may be desirable toremove the xylose, e.g., by chromatography, as some commonly usedmicroorganisms (e.g., yeasts) do not act on xylose. The xylose may becollected and utilized in the manufacture of other products, e.g.,animal feeds and the sweetener Xylitol. The xylose may be removed priorto or after delivery of the sugar solution to the manufacturing facilitywhere fermentation will be performed.

The microorganism can be a natural microorganism or an engineeredmicroorganism, e.g., any of the microorganisms discussed in theMaterials section herein.

The optimum pH for yeast is from about pH 4 to 5, while the optimum pHfor Zymomonas is from about pH 5 to 6. Typical fermentation times areabout 24 to 96 hours with temperatures in the range of 26° C. to 40° C.,however thermophilic microorganisms prefer higher temperatures.

Carboxylic acid groups generally lower the pH of the fermentationsolution, tending to inhibit fermentation with some microorganisms, suchPichia stipitis. Accordingly, it is in some cases desirable to add baseand/or a buffer, before or during fermentation, to bring up the pH ofthe solution. For example, sodium hydroxide or lime can be added to thefermentation medium to elevate the pH of the medium to range that isoptimum for the microorganism utilized.

Fermentation is generally conducted in an aqueous growth medium, whichcan contain a nitrogen source or other nutrient source, e.g., urea,along with vitamins and trace minerals and metals. It is generallypreferable that the growth medium be sterile, or at least have a lowmicrobial load, e.g., bacterial count. Sterilization of the growthmedium may be accomplished in any desired manner. However, in preferredimplementations, sterilization is accomplished by irradiating the growthmedium or the individual components of the growth medium prior tomixing. The dosage of radiation is generally as low as possible whilestill obtaining adequate results, in order to minimize energyconsumption and resulting cost. For example, in many instances, thegrowth medium itself or components of the growth medium can be treatedwith a radiation dose of less than 5 Mrad, such as less than 4, 3, 2 or1 Mrad. In specific instances, the growth medium is treated with a doseof between about 1 and 3 Mrad.

In some embodiments, all or a portion of the fermentation process can beinterrupted before the low molecular weight sugar is completelyconverted to ethanol. The intermediate fermentation products includehigh concentrations of sugar and carbohydrates. These intermediatefermentation products can be used in preparation of food for human oranimal consumption. Additionally or alternatively, the intermediatefermentation products can be ground to a fine particle size in astainless-steel laboratory mill to produce a flour-like substance.

Mobile fermentors can be utilized, as described in U.S. ProvisionalPatent Application Ser. 60/832,735, now Published InternationalApplication No. WO 2008/011598. Similarly, the saccharificationequipment can be mobile. Further, saccharification and/or fermentationmay be performed in part or entirely during transit.

Post-processing

After fermentation, the resulting fluids can be distilled using, forexample, a “beer column” to separate ethanol and other alcohols from themajority of water and residual solids. The vapor exiting the beer columncan be, e.g., 35% by weight ethanol and can be fed to a rectificationcolumn. A mixture of nearly azeotropic (92.5%) ethanol and water fromthe rectification column can be purified to pure (99.5%) ethanol usingvapor-phase molecular sieves. The beer column bottoms can be sent to thefirst effect of a three-effect evaporator. The rectification columnreflux condenser can provide heat for this first effect. After the firsteffect, solids can be separated using a centrifuge and dried in a rotarydryer. A portion (25%) of the centrifuge effluent can be recycled tofermentation and the rest sent to the second and third evaporatoreffects. Most of the evaporator condensate can be returned to theprocess as fairly clean condensate with a small portion split off towaste water treatment to prevent build-up of low-boiling compounds.

Intermediates and Products

Using the processes described herein, the treated biomass can beconverted to one or more products, such as energy, fuels, foods andmaterials. Specific examples of products include, but are not limitedto, hydrogen, alcohols (e.g., monohydric alcohols or dihydric alcohols,such as ethanol, n-propanol or n-butanol), hydrated or hydrous alcohols,e.g., containing greater than 10%, 20%, 30% or even greater than 40%water, xylitol, sugars, biodiesel, organic acids (e.g., acetic acidand/or lactic acid), hydrocarbons, co-products (e.g., proteins, such ascellulolytic proteins (enzymes) or single cell proteins), and mixturesof any of these in any combination or relative concentration, andoptionally in combination with any additives, e.g., fuel additives.Other examples include carboxylic acids, such as acetic acid or butyricacid, salts of a carboxylic acid, a mixture of carboxylic acids andsalts of carboxylic acids and esters of carboxylic acids (e.g., methyl,ethyl and n-propyl esters), ketones (e.g., acetone), aldehydes (e.g.,acetaldehyde), alpha, beta unsaturated acids, such as acrylic acid andolefins, such as ethylene. Other alcohols and alcohol derivativesinclude propanol, propylene glycol, 1,4-butanediol, 1,3-propanediol,methyl or ethyl esters of any of these alcohols. Other products includemethyl acrylate, methylmethacrylate, lactic acid, propionic acid,butyric acid, succinic acid, 3-hydroxypropionic acid, a salt of any ofthe acids and a mixture of any of the acids and respective salts.

Other intermediates and products, including food and pharmaceuticalproducts, are described in U.S. Ser. No. 12/417,900, the full disclosureof which is hereby incorporated by reference herein.

EXAMPLE

A sheared paper feedstock was prepared as follows:

A 1500 pound skid of virgin, half-gallon juice cartons made ofun-printed polycoated white Kraft board having a bulk density of 20lb/ft3 was obtained from International Paper. Each carton was foldedflat, and then fed into a 3 hp Flinch Baugh shredder at a rate ofapproximately 15 to 20 pounds per hour. The shredder was equipped withtwo 12 inch rotary blades, two fixed blades and a 0.30 inch dischargescreen. The gap between the rotary and fixed blades was adjusted to 0.10inch. The output from the shredder resembled confetti having a width ofbetween 0.1 inch and 0.5 inch, a length of between 0.25 inch and 1 inchand a thickness equivalent to that of the starting material (about 0.075inch).

The confetti-like material was fed to a Munson rotary knife cutter,Model SC30. Model SC30 is equipped with four rotary blades, four fixedblades, and a discharge screen having ⅛ inch openings. The gap betweenthe rotary and fixed blades was set to approximately 0.020 inch. Therotary knife cutter sheared the confetti-like pieces across theknife-edges, tearing the pieces apart and releasing a fibrous materialat a rate of about one pound per hour. The fibrous material had a BETsurface area of 0.9748 m²/g+/−0.0167 m²/g, a porosity of 89.0437 percentand a bulk density (@0.53 psia) of 0.1260 g/mL. An average length of thefibers was 1.141 mm and an average width of the fibers was 0.027 mm,giving an average L/D of 42:1.

To saccharify the paper feedstock, first 7 liters of water was added toa vessel. The temperature of the water was maintained at 50° C.throughout the saccharification process, and pH was maintained at 5. Thefeedstock was added to the water in increments, as shown in the tablebelow. After each addition, mixing was performed until the feedstock wasdispersed, after which a mixture of two enzymes was added, again asshown in the table below. (Enzyme 1 was Accellerase® 1500 enzymecomplex. Enzyme 2 was Novozyme™ 188 cellobiase enzyme.) After eachaddition, mixing was initially performed at 10,000 RPM, with the mixerbeing turned down to 4,000 RPM as soon as the feedstock had beendispersed. An IKA Werks T-50 jet agitator mixer was used, with a50K-G-45 jet mixing tool.

The feedstock was added in increments because it was necessary to atleast partially saccharify the feedstock before more could be added;otherwise the mixture became too difficult to mix. It was observed thatless enzyme was needed to obtain a given glucose level than had beenrequired in previous shake-flask experiments. No contamination byundesirable microorganisms such as mold was observed for the first 300hours. At approximately 300 hours a mold-like organism was observed onthe tank walls where sugar concentration was lowest, but not in the tankitself.

Glucose Glucose Paper Time (Measured (Calculated Enzyme 1 Enzyme 2feedstock (hr) (g/L)) (g/L)) (ml) (ml) (g) 0 0.548 54.8 100 10 400  70.641 64.1 100 10 400  25 0.779 77.9 100 10 300  29 0.8 80 0 0 0 50 1.11111 100 10 300  55 1.25 125 0 0 0 75 1.39 139 200 20 1600*  80 1.71 1710 0 0 82 1.88 188 0 0 0 106 2.03 203 0 0 0 130 2.32 232 0 0 0 150 2.75275 0 0 0 *The 1600 gram addition was made over the course of severalhours.

Other Embodiments

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure.

For example, the jet mixers described herein can be used in any desiredcombination, and/or in combination with other types of mixers.

The jet mixer(s) may be mounted in any desired position within the tank.With regard to shaft-mounted jet mixers, the shaft may be collinear withthe center axis of the tank or may be offset therefrom. For example, ifdesired the tank may be provided with a centrally mounted mixer of adifferent type, e.g., a marine impeller or Rushton impeller, and a jetmixer may be mounted in another area of the tank either offset from thecenter axis or on the center axis. In the latter case one mixer canextend from the top of the tank while the other extends upward from thefloor of the tank.

In any of the jet mixing systems described herein, the flow of fluid(liquid and/or gas) through the jet mixer can be continuous or pulsed,or a combination of periods of continuous flow with intervals of pulsedflow. When the flow is pulsed, pulsing can be regular or irregular. Inthe latter case, the motor that drives the fluid flow can be programmed,for example to provide pulsed flow at intervals to prevent mixing frombecoming “stuck.” The frequency of pulsed flow can be, for example, fromabout 0.5 Hz to about 10 Hz, e.g., about 0.5 Hz, 0.75 Hz, 1.0 Hz, 2.0Hz, 5 Hz, or 10 Hz. Pulsed flow can be provided by turning the motor onand off, and/or by providing a flow diverter that interrupts flow of thefluid.

While tanks have been referred to herein, jet mixing may be used in anytype of vessel or container, including lagoons, pools, ponds and thelike. If the container in which mixing takes place is an in-groundstructure such as a lagoon, it may be lined. The container may becovered, e.g., if it is outdoors, or uncovered.

While biomass feedstocks have been described herein, other feedstocksand mixtures of biomass feedstocks with other feedstocks may be used.For example, some implementations may utilize mixtures of biomassfeedstocks with hydrocarbon-containing feedstocks such as thosedisclosed in U.S. Provisional Application No. 61/226,877, filed Jul. 20,2009, the full disclosure of which is incorporated by reference herein.

Accordingly, other embodiments are within the scope of the followingclaims.

1. A method comprising: saccharifying a biomass feedstock in a vessel bymixing the biomass feedstock with a fluid medium and a saccharifyingagent using a jet mixer.
 2. The method of claim 1 wherein the feedstockhas a bulk density of less than about 0.5 g/cm³.
 3. The method of claim1 wherein the fluid medium comprises water.
 4. The method of claim 1wherein the saccharifying agent comprises an enzyme.
 5. The method ofclaim 1 wherein the jet mixer comprises a jet-flow agitator, and whereinsaccharifying the feedstock comprises agitating the feedstock with thejet-flow agitator.
 6. The method of claim 5 wherein the jet-flowagitator comprises an impeller mounted at a distal end of a shaft, and ashroud surrounding the impeller.
 7. The method of claim 5 wherein thejet mixer comprises a plurality of jet-flow agitators, each jet-flowagitator being configured to operate reversibly, pumping fluid towardsthe top of the vessel in a first mode, and towards the bottom of thevessel in a second mode.
 8. The method of claim 7 wherein, during atleast part of mixing all of the jet-flow agitators are operated in thefirst mode.
 9. The method of claim 7 wherein, during at least part ofmixing some of the jet-flow agitators are operated in the first modeand, at the same time, others are operated in the second mode.
 10. Themethod of claim 7, further comprising adding a microorganism to thevessel and fermenting the saccharified feedstock, wherein during atleast part of fermentation all of the jet-flow agitators are operated inthe first mode.
 11. The method of claim 1 wherein the vessel has anarcuate bottom surface.
 12. The method of claim 1 wherein the jet mixercomprises a jet aeration type mixer having a delivery nozzle, andwherein saccharifying the feedstock comprises delivering a jet throughthe delivery nozzle.
 13. The method of claim 12 wherein the jet mixer isoperated without injecting air through the delivery nozzle.
 14. Themethod of claim 12 wherein saccharifying comprises supplying a liquid totwo inlet lines of the jet aeration type mixer.
 15. The method of claim1 wherein the jet mixer comprises a suction chamber jet mixer.
 16. Themethod of claim 1 wherein the jet mixer comprises a nozzle in fluidcommunication with a first end of an ejector pipe, the first end of theejector pipe being spaced from the nozzle, and the ejector pipe having asecond end that is configured to emit a fluid jet.
 17. The method ofclaim 1 wherein saccharifying comprises adding the feedstock to thefluid medium in discrete increments; and mixing each discrete incrementof feedstock into the fluid medium with the jet mixer before addinganother increment of feedstock.
 18. The method of claim 1 furthercomprising monitoring a glucose level of a mixture of the feedstock, thefluid medium and the saccharifying agent during operation of the jetmixer.
 19. The method of claim 1 further comprising adding additionalfeedstock and saccharifying agent to the vessel during saccharification.20. The method of claim 1 wherein the vessel comprises a tank.
 21. Themethod of claim 1 wherein the vessel comprises a tank of a rail car or atanker truck.
 22. The method of claim 21 wherein saccharification takesplace partially or completely during transport of the mixture offeedstock, fluid medium and saccharifying agent.
 23. The method of claim1 wherein the feedstock comprises a cellulosic or lignocellulosicmaterial.
 24. The method of claim 23 wherein the feedstock comprisespaper.
 25. The method of claim 1 further comprising adding an emulsifieror surfactant to the mixture in the vessel.
 26. The method of claim 1further comprising adding a microorganism to the vessel and fermentingthe saccharified feedstock.
 27. A method comprising: saccharifying abiomass feedstock by operation of a mixer that produces generallytoroidal flow within a vessel in which the biomass feedstock has beenplaced with a fluid medium and a saccharifying agent.
 28. The method ofclaim 27 wherein the mixer is configured to limit any increase in theoverall temperature of the fluid medium to less than 5° C. over thecourse of mixing.
 29. A method comprising: converting a low molecularweight sugar to a product by mixing the low molecular weight sugar witha microorganism in a fluid medium, using a jet mixer.
 30. The method ofclaim 29 wherein the fluid medium comprises water.
 31. The method ofclaim 29 wherein the microorganism comprises yeast.
 32. The method ofclaim 29 wherein the jet mixer comprises a jet-flow agitator, andwherein converting comprises agitating the feedstock with the jet-flowagitator.
 33. The method of claim 29 wherein the jet mixer comprises ajet aeration type mixer having a delivery nozzle, and whereinsaccharifying the feedstock comprises delivering a jet through thedelivery nozzle.
 34. The method of claim 29 wherein the jet mixercomprises a suction chamber jet mixer.
 35. A feedstock saccharificationapparatus comprising: a tank, a biomass feedstock delivery deviceconfigured to deliver a biomass feedstock to the tank, and asaccharifying agent delivery device configured to deliver a meteredamount of a saccharifying agent to the tank, and a jet mixer having anozzle disposed within the tank and configured to mix the deliveredbiomass feedstock and saccharifying agent.
 36. The apparatus of claim 35wherein the jet mixer further comprises a motor, and the apparatusfurther comprises a torque monitor that monitors torque of the motorduring mixing, and/or an amp monitor that monitors the full loadamperage of the motor.
 37. The apparatus of claim 35 further comprisinga controller that adjusts the operation of the feedstock delivery deviceand/or the saccharifying agent delivery device based on input from thetorque monitor.
 38. The apparatus of claim 35 wherein the jet mixercomprises a motor and the apparatus further comprises a variablefrequency drive configured to adjust the speed of the motor.
 39. Theapparatus of claim 35 wherein the tank has an arcuate bottom surface.40. A method comprising: saccharifying a biomass feedstock in a vesselto form a saccharified mixture; inoculating the saccharified mixture inthe vessel with a microorganism; and allowing the inoculatedsaccharified mixture to ferment in the vessel.
 41. The method of claim40 further comprising, during fermentation, transferring the contents ofthe vessel to a transport vessel and allowing fermentation to continuein the transport vessel.
 42. The method of claim 40 further comprisingagitating the contents of the vessel with a jet mixer duringsaccharification and fermentation.
 43. The method of claim 40 furthercomprising monitoring the oxygen content and ethanol and/or sugarcontent of the fermenting mixture.
 44. A fermentation system comprising:a vessel having a vent; a source of oxygen in communication with thevessel; an oxygen monitor configured to monitor the oxygen content of aliquid in the vessel; and a controller configured to adjust the oxygencontent of the liquid, using the vent and oxygen source, in response toinput from the oxygen monitor.
 45. The fermentation system of claim 44wherein the controller is configured to oxygenate the vessel at a rateof less than 0.2 vvm.
 46. The fermentation system of claim 44 furthercomprising a fermentation monitor configured to monitor the sugarconcentration and/or ethanol concentration of the liquid in the vessel;and a controller configured to stop fermentation based on input receivedfrom the fermentation monitor.
 47. The fermentation system of claim 46further comprising a fermentation stopping module configured to stopfermentation in response to a signal received from the controller.